An Account of the Measurement of an Arc of the Meridian, Extending from Dunnose, in the Isle of Wight, Latitude 50 degrees 37^′ 8^{′ ′}, to Clifton, in Yorkshire, Latitude 53 degrees 27^′ 31^{′ ′}, in Course of the Operations Carried on for the Trigonometrical Survey of England, in the Years 1800, 1801, and 1802

XVI. An Account of the Measurement of an Arc of the Meridian, extending from Dunnose, in the Isle of Wight, Latitude $50^\circ 37' 8''$, to Clifton, in Yorkshire, Latitude $53^\circ 27' 31''$, in course of the Operations carried on for the Trigonometrical Survey of England, in the Years 1800, 1801, and 1802. By Major William Mudge, of the Royal Artillery, F. R. S. Read June 23, 1803. SECTION FIRST. In the last account presented to the Royal Society, I expressed my intentions of making the operations which were to follow that period, subservient to the purpose of measuring a portion of the meridional arc, running from Dunnose, in the Isle of Wight, into the northern part of Yorkshire. In the account referred to, (See Phil. Trans. for 1800, page 565,) I stated my reasons for adopting that resolution, and my hopes that Mr. Ramsden would shortly finish the zenith sector which his Grace the Duke of Richmond had bespoken of him, when Master General of the Ordnance. As that celebrated artist, from the beginning of the year 1800 till the middle of the following summer, had proceeded with little interruption, except from illness, towards its completion, the whole was brought so near to a conclusion before he died, that Mr. Berge found no difficulty in rendering it sufficiently perfect. It is proper I should state, more fully than I have formerly done, my reasons for selecting Dunnose as one of the extremities of my meridional line, and also those for preferring its meridian to any other; which I shall do as briefly as possible. In a country whose surface, throughout its whole extent, is equally diversified with hilly ground, that particular part of it should be chosen, for carrying on a meridional measurement, which comprehends the most extensive arc. This arises from the necessary consequence which attends an operation in a country so circumstanced; as, possibly, no spot fixed on for a place of observation, could be supposed free from the effects of the unequal attraction in the adjoining matter. In such a country, therefore, a measurement upon the most extensive arc, must give the most accurate conclusion; for the errors arising from the cause here mentioned, like those of observation, lessen in their effects, on their application to arcs of increasing magnitude. If Great Britain were a country thus diversified, the most eligible part would be that where the meridian from Lyme, in Dorsetshire, passes northward into Scotland. The difference of latitude between that place and Aberdeen, near to which that line cuts its parallel, is $4^\circ 47'$, nearly. But, however great the advantages attending such a length of arc might be, under the general circumstances of accurate terrestrial measurement, and accurate observations at its extremities, no beneficial consequences could be expected to attend the placing of the sector at intermediate stations; as the arc would be found running, almost everywhere, through a country abounding with hills, considerable both in magnitude and number. Under this consideration, I determined to measure a portion of the meridian which proceeds from Dunnose to the mouth of the Tees; because, from inquiry, I had reason to suppose it the longest meridional arc in Britain, free from any apparent obstruction. And I was led to select Dunnose for one of its extremities, as observations made there, in conjunction with others at Greenwich, would enable me to make corrections of the latitudes of places given in our former papers, if found necessary. By fixing on Dunnose, I had also the means of ascertaining the distance of the Royal Observatory from the northern or southern end of my line, and, consequently, of connecting it with the parallels of Dunkirk and Paris. Dunnose being fixed on, my subsequent endeavours were directed towards carrying on the triangles, as nearly as I possibly could, in the direction of its meridian, selecting the stations so that their sides might be properly inclined to it, and of sufficient length. In choosing the station at the northern extremity, I was careful to select it as near the meridian of the southern one as possible, and likewise in the neighbourhood of some open spot of ground, proper for the measurement of a base of verification. A station having these advantages, was found near Clifton, a small village in the vicinity of Doncaster; and a level of sufficient extent for a base, on Misterton Carr, in the northern part of Lincolnshire. In the composition of this account, I wish to confine myself to that part of my operations which relates merely to the matter expressed under its title. I am possessed of materials sufficient for another Paper; and shall give about thirteen hundred triangles, principal and secondary, when next I present an account of the Survey to the Society: professing this, I shall now say, that in 1800 and 1801, the angles of the triangles constituting the meridional series were observed; and that, in the latter year, the new base was measured on the abovementioned Carr. I should not omit mentioning in this article, that while the instrument was at Clifton, the direction of the meridian was obtained from numerous observations on the pole star, at the times of its greatest eastern and western elongations from the meridian. It will be recollected, that similar observations were made at the station on Dunnose, in 1793; (see Phil. Trans. for 1795, page 460;) so that nothing relating to the terrestrial part of the operation remained to be performed at the expiration of 1801. On my arrival in town, after the measurement of the base of verification in the north, I had the happiness of finding the zenith sector nearly completed. Little remained to be done, besides the dividing of its arch; an operation which Mr. Berge proposed to defer till the following spring: it was then divided, and the instrument, being otherwise complete, was delivered into my hands in April. An observatory of convenient form having been previously made, the sector was immediately erected in the Tower; and, from thence, with the permission of Dr. Maskeleyne, it was sent to the Royal Observatory at Greenwich. It is now necessary I should enter into a minute detail of this instrument's construction, giving a description of its several parts, with references to proper drawings. If, indeed, I had no other motives, I should perhaps be induced to do it from justice to the merit and memory of the ingenious inventor; who seems to have exerted his talents to the full extent of the hopes he entertained, of rendering this instrument the first of its kind. General Description of the Zenith Sector. In the sector I am going to describe, Mr. Ramsden has obviated the inconveniences attendant on the use of former sectors; and has also diminished, in a very considerable degree, the errors unavoidably resulting from their imperfect construction. The principles on which he has founded the several improvements, consist in the means of uniting the sectorial tube to its axis, so as to ensure the permanency of the length of its radius, when erected for observation; more accurate methods of adjusting the instrument vertically; and an easy way of placing the face of its arch in the plane of the meridian. Another circumstance of moment was, some contrivance by which the plumb-line should be brought precisely over the point, marking the centre of the circle of which the divided arch of the sector should be a part. The last desideratum, the ingenious artist procured, by applying the same contrivance which so eminently displayed his skill, in the construction of the quadrant belonging to his Grace the Duke of Marlborough; a contrivance by which the plumb-line can be as readily adjusted over the required point, by a person standing on the ground, as any adjustment, or other act within his reach, can be performed. A description of this, as well as of the means by which the instrument is rendered vertical, and otherwise correctly prepared for observation, will be given, with the assistance of plates. Plate IX. Exhibits a general view of the sector erected for observation: it consists of two parts; 1st, the frame which supports the apparatus to which the sectorial tube is attached; 2d, the work constituting that apparatus, with the tube itself. The external frame or stand is made of mahogany, and unites strength with simplicity of construction. In shape, it is an ob-truncated pyramid, whose base is a square of six feet in length, and whose vertex is half of it. This frame, although light in its make, is yet, when united by means of square-headed screws, sufficiently firm. Inside this hollow stand is erected another frame, of the same substance, strong and well made, within which is suspended the sector; its frame being supported at top in every lateral direction, and sustained at bottom by a cone resting in a metallic concavity, the figure of which may be imagined, by supposing an arch of a circle to revolve round a tangent to one of its extremities. A cylinder, in the upper part of the interior stand, finds its place in an opening of an octagonal shape in the exterior frame, and, by a simple contrivance, is retained in that situation, while the sector and apparatus revolves on the cone. Thus, a ready means presents itself of turning the instrument round, with the face of its divided arch towards the east or west. It may be steadily retained in any position, by clamping it to the brass work of an azimuth circle, attached to the bottom of the external frame. The direction of the meridian, at the place of observation, having been previously obtained from double azimuths of the pole star, this instrument admits of being placed in that direction very accurately. A telescope, twenty-nine inches in length, is attached to the side of the great tube, or rather, may be occasionally placed on a frame permanently fastened to it, having its axis in the plane of the divided arch, and very nearly at right angles to its radius. On the divided azimuth circle below, the angular bearing of any proper object may be set off, by turning the sector round till that object bisects the cross wires in the little telescope, and then noting the vernier. If the axis of the sector be horizontal, and the interior frame set perfectly upright, the instrument may be turned round from one point of the compass to the other, and properly adjusted for observation, in a few minutes. In this general description, I am now to speak of one of the most ingenious contrivances attending the sector, which is, the means of readily adjusting the plumb-line in its several positions. I refer to the Plates and their descriptions, for a full account of it; but, as it will enable the reader to understand that which represents the instrument in its perspective view, (Plate IX.) I shall shortly describe this part. The telescope of the sector is nearly eight feet long, and has an object-glass of four inches in diameter. It is attached to an axis, similar in shape to that of a transit-instrument, having at one end a lens, and near to the tube an arrangement of brass work, carrying a thin and diaphanous slice of mother-of-pearl, having, as appears to the naked eye, a dot upon it. The centre of this dot is by construction the true centre of the conical axis, and consequently of the circle of which the divided limb is a part. It is unnecessary to say, in this place, how that diaphragm was so adjusted as to have the centre of its dot where it should be, or the means by which it has been permanently fixed; it suffices that I say the point was placed most accurately, and the diaphragm fastened so firmly in the cone, that no readjustment of this part has been found necessary, since the sector came into my hands. As the axis is hollow, a light, as that of a candle, held at its open end, is transmitted through the mother-of-pearl, which, stopping a part of its rays, exhibits a circle of red light to an eye looking through the lens at the opposite end of the axis; a well defined and exceedingly small dot appearing in the middle of the illuminated circle. Through proper openings in the upper and under parts of the axis, and suspended from a point not connected with it, passes the plumb-line, having its position by construction close to the dot; so that, by looking through the axis in this way, the plumb-line appears like a small black line on the face of the mother-of-pearl. Now it is evident that, to an eye thus placed, when the instrument is adjusted for observation, the plumb-line should appear as if accurately bisecting the dot. To give, therefore, the observer the means of moving it to the right or left, when standing on the ground, (avoiding thereby the inconvenient necessity of elevating himself on steps as high as the axis,) Mr. Ramsden placed a microscope, about 5 feet in length, parallel to the telescope, on the outside of the interior mahogany frame. This microscope, bent as it were at right angles at both ends, has one of them open, and placed close to the pivot of the axis carrying the small lens. In the upper part of the microscope, and just under its roof, is placed a speculum, inclined, at an angle of $45^\circ$, to the line passing through the centre of the sector's axis, and close to its end. This reflector receives the converged images of the dot and wire on the illuminated spectrum, and transmits them down the tube of the long microscope: the rays, falling on a plano-convex glass, at no great distance from the bottom, are finally sent out to the eye by a prismatic glass at the end of the tube. Thus viewed, that which to the naked eye above appeared a small dot on the illuminated lamina, when magnified, as delivered below, is seen to be a small and well defined circle with a luminous area, admitting of the most accurate means of deciding on the right position of the plumb-line, by exhibiting small portions of light between it and the periphery of the little circle. The mode of illuminating the hollow axis is likewise ingenious. On the side of the interior mahogany frame, and opposite to the vertical microscope, is suspended a lamp on two arches. At the back of it is a hollow cylindrical recess, in which is placed a polished metallic segment of a sphere. This concave reflector is attached to the cylinder, by means which give it any position required; so that the image of the burning wick, in the hollow of the lamp, may be thrown at pleasure on any spot above. From the end of the conical axis, on the same side with this lamp, projects a small brass arm, carrying at its extremity a speculum, whose surface is placed at $45^\circ$ with the vertical, and directly opposite the open end of the sector's axis. When the image of the burning wick is thrown from the concave reflector on the flat one above, the light passes through the hollow axis, illuminating the mother-of-pearl, and is, at last, sent down the microscopic tube to the eye below. This contrivance, collectively taken, is unique, and is full as accurate in its operation as ingenious in itself. From its nature, granting perfection of work, there can be no parallax between the dot and the wire. The images of the illuminated circle and wire, (plumb-line,) are coincident on the upper surface of the prismatic eye-glass, and transmitted so. In short, the whole has been so well managed, that the plumb-line can be made to bisect the dot or little circle, as accurately as the points on the divided limb of the sector. I consider this general description of this part of the instrument sufficient for the present; the proper plate, and its appropriate explanation, will supply what yet remains to be said. The plumb-line is suspended above the upper part of the axis, from a point connected with the extremity of a bent lever, moveable round its fulcrum. The other end of the lever is acted on by a helical spring, which presses downwards, and causes it to bear against a screw passing through a head of metal beneath that end. The extremity of the long screw is square, and has its place in a pipe attached to a mahogany rod, divided in the middle by a universal joint. One extremity of this rod is brought down, and received in a socket within convenient reach of the observer, who, looking at the image of the dot and wire, turns the rod, thus connected with the bent lever, and thereby gives motion to the plumb-line. The pivots of the sector's axis are of bell metal, ground perfectly true and smooth. They rest in Ys, firmly attached to the upper part of the frame. The method of uniting the plates carrying those Ys, is as follows: at the upper part of the mahogany frame are four hollow strong cylinders of brass, which pass through the wooden work, and, at the same time, serve to connect very firmly the two sides of the upper part of the frame. These cylinders project about six inches beyond the surface of the wood, and have screws and nuts at their ends. The brass plates furnished with the Ys, have four holes in each of them, which answer to the ends of the screws, and are attached to the cylinders furnished with those screws, by the respective nuts. In the Ys, the pivots of the axis are placed; and, as a means of adjusting each Y is fixed to each plate, any position, within a certain limit, may be assigned to the sector and its axis. To prevent the pivots of the axis from moving to and fro in a sidelong direction, Mr. Ramsden adopted a contrivance for keeping them, at all times, in the same constant position in the Ys. This desideratum was not to be dispensed with; for, if the ends of the axis, from the thickening of the oil, or the accumulation of dust, should work laterally in their angles, the distance between the plumb-line and arch would be continually varying; a perplexing evil, and the cause of great inaccuracy. The sum of this contrivance consists, first, in one of the Y plates having a small piece of brass screwed flat upon it, with a roller or friction-wheel at its end, which reaches just high enough to meet the vertical surface of the pivot a small distance within its circumference; and, secondly, in the other Y plate having a small apparatus, consisting of a lever furnished with another friction wheel and a spring, at its other extremity. This last mentioned roller, from the spring's action, presses against its proper pivot, and thrusts the other against the fixed wheel. By these simple but ingenious means, the axis is always retained in its proper situation with respect to the Ys. To prevent the axis from bending, by the preponderance of the telescope and arches, Mr. Ramsden added braces and counterpoising weights. The braces are four in number, each being a hollow tube: they are fastened both to the axis and the telescope. Their principal uses consist in obviating the possibility of the telescope bending from accidental pressure, or vibrating when lightly touched. The method of preventing the telescope from sinking, or, in other words, the axis from bending, is by the use of levers and the abovementioned weights. These levers, two in number, are attached to the interior mahogany frame at top, the fulcrum of each being immovable. At the end of each lever farthest from the tube, a weight is suspended, from a hook capable of being placed nearer to, or farther from, the fulcrum, at pleasure; thereby affording the means of raising the other end of the lever up against the cone, with any required degree of force. That extremity of the lever, so pressing upwards, has two large friction-wheels, which apply themselves to the sides of the conical axis, but do not retard the free motion of it, when the telescope is moved in the direction of the plane of its arch. These wheels, two on each lever, support the axis near the junction of the telescopic tube; and, as a few ounces only are by these means suffered to press on the pivots, no bending takes place in the cones. From the middle of the two uppermost horizontal cylinders, which unite the sides of the interior frame at top, and which receive, with the two beneath them, the respective Y plates, arises a small but substantial apparatus of metal, embracing a hollow brass cylinder, of five inches in diameter, and about three deep, which passes up into an opening in the upper part of the external mahogany frame. This cylinder, with its corresponding stand, are sustained, without any sort of shake, by a helical spring. This mode, with that of supporting the azimuth circle below, are so well managed, that when the instrument is properly adjusted for observation, the axis of the sector continues perfectly horizontal, in every position of the frame. There is likewise a very convenient method of sustaining the sectorial tube in any required position for observation. Across the interior frame, about the height of the graduated arch, run two long brass axles, with two wheels on each, one precisely in the middle of the axle, (and consequently in the same plane with the line vertically cutting the middle of the telescope,) and the other close to the pinion at the end of the axle. From a steel pin, something peculiar in its construction, situated near the end of the telescope, proceeds a string, which is wound eight or ten turns round the pulley. Attached to the inside of the interior frame, and just above the wheels nearest to the end of the axle, is another pulley, over which, passing into a long and narrow wooden compartment, is thrown a string, having a hook and a proper apparatus for receiving the moveable weights. The other end of this string is fastened to the pulley close to the axle, and gives motion to the telescope, or retains it in equilibrio, according to the arrangement of the two sets of weights, which consist of fifteen pieces of brass. By these means, all injurious pressure is taken off the point of the micrometer-screw, against which the telescope may be made to bear, with any required degree of force. To cause the string passing over the middle of the pulley to draw in the exact direction of the limb's plane, Mr. Ramsden placed four small friction-wheels close to the eye end of the telescope, two on each side, and between each pair of wheels a steel pin, made like a T, with a hook at the end, to receive a string. This pin, where it applies to the wheels, is something in shape like a double cone, and is passed behind them. It always, from its construction, assumes the same position with regard to the friction-wheels; from which circumstance, the sustaining string is ever found in the plane passing through the centre of the telescope and the middle of the pulley. The micrometer-screw, for measuring minutes and seconds, performs its operations in the usual way: it is moved backwards or forwards on a brass arch, parallel to the limb of the sector, and placed against the mahogany frame behind. To this arch the apparatus carrying the micrometer-screw is clamped; and it is adjusted, or brought parallel to the limb, by screws, so that the point of the micrometer-screw always bears exactly on the same part of the polished steel head, at the end of the sector. The principal wires in the focus of the eye-glass are two, and are at right angles to each other. There are, indeed, two others parallel to the meridional one, and at equal distances from it; they were placed there with a view of rendering an adjustment of the horizontal wire sufficiently easy. These are illuminated by means of the lamp which carries the concave reflector before spoken of. There is a hole, with a lens, in the side of the telescope, directly opposite to the lamp, having behind it a diaphragm of brass, coated with plaster of Paris, and inclined to the vertical axis of the tube, at an angle of 45 degrees. The quantity of light, suited to the circumstances of the observation, is regulated by coloured glasses, placed over the hole in the side of the tube. The plummet, suspended at the wire, falls into a cylindrical cup, swinging by two pins on its edge, on the extremity of a brass frame annexed to the interior stand; which frame is capable of being raised or lowered at pleasure by a milled-headed screw; so that the wire can, at any time, be released from the weight of the plummet, by screwing up the vessel containing it. There are two arches attached to the end of the tube, one on each side of it, and firmly united together by means of brass pillars; which arrangement effectually secures the divided arch from injury. The total extent of the arch is about $15^\circ$, having half of its subtense on each side zero. It is divided into every 5 minutes; the micrometer-screw measuring any supplementary quantity. Golden pins were let into the arch, by the advice of the Astronomer Royal, on which the divisions were laid off by Mr. Berge, in a very masterly and accurate manner, as will be seen hereafter. A magnifier, whose focal distance is about half an inch, is placed under the bottom of the cross piece opposite to the arch, and is furnished with a horizontal adjustment for bringing it directly over the plumb-line. Among the various eye-pieces, of different magnifying powers, is one furnished with a prism. This, necessarily bent at right angles, enables the observer to see the stars without touching the frame. The use of it has been found convenient; but habit and proper caution enable the astronomer to use either of the other glasses. Having given this cursory and general description of the instrument, as seen at first view, I shall proceed to an explanation of the plates, which show its various parts. **Particular Description of the Zenith Sector.** Plate X. Represents a general section of the instrument and stand. AB is one of the four great uprights of the external mahogany frame, and CB its top, having an opening in D, for admission of light. The uprights consist of two strong pieces, firmly screwed together; each upright having seven strong screws, as seen in the upright AB. The top may be considered as a sort of square table, screwed down on the upper part of the frame. Between each of the two uprights is a brace, diagonally fixed, for strengthening the stand, as may be seen in the plate; and four others go horizontally, from upright to upright, for the purpose of still farther strengthening the whole. Across the bottom of the frame, and exactly in the middle of it, is a very strong mahogany plank, whereon rests the sector, having a stout straight edge bar of the same substance underneath. In the middle of this cross piece, as seen at E, is an apparatus of brass, furnished with an azimuth circle, having a hollow receptacle of bell-metal in the centre, in which rests, on a conical point, the interior mahogany frame FGHI. This brass work, which is strong and substantial, may be seen in Plate XIV. It is there represented *in plano*, with the bottom part of the interior stand placed above it. The means of making the interior stand vertical, are found in the work annexed to the azimuth circle. They consist of two screws, attached to two plates of brass, placed at right angles to, and also flat on each other. $S_s$ (Plate XIV.) are the screws. A vernier on the divided circle may be seen at $S$; and at $s$, the method of clamping the bottom of the stand. On the opposite side is another provision for clamping this stand, when the face of the sector is changed from east to west, or vice versa. KLMNO$p$ (Plate X.) is a section of the telescope and axis, MR, MR, being two of the four braces for strengthening the axis, and steadying the telescope. K is the place of the eyetube; L the elliptical reflector for illuminating the wires at K; and ON a hollow cylinder of brass, independent of the tube. In the upper part of this cylinder, the object-glass is rivetted; the cylinder itself being fastened to the great eye-tube, in a permanent manner. W, W, are two weights, hanging freely from the ends of two levers, the opposite ends being furnished with four friction-wheels. The points of support, between the weights and wheels, are at TT, being at the extremities of two upright solid pieces of metal, which are moved up or down by the screws beneath them. These counterpoising weights prevent any bending of the axis, between the pivots and those parts to which they apply. The apparatus for carrying the levers, is attached to the inside mahogany frame by screws, as represented in the section. See also Plate XIII. The plummet and plumb-line are seen at $aed$; the point of suspension being $a$, and the plummet $d$; the plumb-line passing close by the arch, whose section is $bc$, and also near to the dot or small circle $e$, described on the thin slice of mother-of-pearl, shown in the section of the axis at $e$. A lamp is attached, or rather rests, on circular supports annexed to the side of the interior frame, and may be seen at XZ. At the back of the lamp, placed in a recess, is a concave reflector at $Z$; and, in the front of it, a tube running out to $X$, having a double convex glass at $P$, for throwing the light on $L$, which first passes through a double concave glass in the side of the telescope, and then, from the reflector $L$, is thrown down on the wires near $K$. The concave speculum $Z$, has two adjustments for converging the reflected light on the little elliptical speculum $b$. This last-mentioned speculum throws off the said light at $b$, which passes into the axis at $G$, illuminating the mother-of-pearl at $e$, and, finally, is transmitted out of the axis at $p$. $k l m n$, is a section of the long microscope, for conveying the image of the dot and wire, sent out of the axis at $p$, to the eye at $k$. This microscope is firmly attached to the side of the frame, by brass cylinders, $k k$, $l l$, $m m$, $n$, and has one plano-convex glass at $q$, a prismatic eye-glass at $u$, and a metallic reflector at the top, $o$. At the upper end of this long microscope, and directly behind the speculum, is a screw, by which the reflecting metal is brought into one of its requisite positions. The other adjustment of that metal is performed by two screws, which apply to the sides, and give it lateral motion. The plano-convex glass at $q$, is rivetted into the head of a long tube $u q$, which slides up the microscope. The upper part of the microscope at $o$, is placed exactly opposite the end of the axis, in a very firm way. The rod for giving motion to the plumb-line, is $v w x$; $v$ being the top of it, $w$ the place of the universal joint, which separates the two parts of the rod, and $x$ the bottom of the rod. itself, to which part the hand is applied. In this section, the top \( v \) is not furnished with the pipe connecting it with the bent lever above; but the representation of it, together with the lever itself, and accompanying spring, will be understood by referring to the plate which contains a representation of those parts. In Plate XII. is a section of the axis passing through the pivots, and one exhibiting the face of the several united planes constituting the diaphragm, which adjust, in every direction, the slice of mother-of-pearl. Above this latter, is a view of the lever which gives motion to the plumb-line, with the pipe, spring, &c.; these are represented as seen from an eye at one of the pivots; and, above the other section, is a view of the same apparatus, seen in a direction at right angles to the former one. In the latter of the above-mentioned sections, \( bab \) is the diaphragm, having in the middle, as at \( p \), a circular piece of mother-of-pearl, extremely thin, with a small dot in the centre. This brass work is annexed to the large end of a hollow conical piece of brass, which exactly fits the axis at its proper place. It is there screwed fast, and may be considered as of one piece with the axis. In the adjoining figure, \( bfl \), is a section of the cone, \( p \) being the place in the opening of the brass work which receives the mother-of-pearl. In the representation of the diaphragm, \( a \) and \( b \) are two screws, at right angles to each other, and respectively attached to flat pieces of metal which slide on each other. If \( fb \) represent the plumb-line, the direction of each screw is that of an angle of 45 degrees with it. By means of these adjusting screws, the dot or little circle at \( p \) was placed in its proper position, or in the centre of the circle \( abb \); so that, on an adjustment of the plumb-line, in any one position of the instrument, the dot still remains accurately bisected, however the telescope be subsequently moved. Above $abb$, is a small frame-work of brass, from which the plumb-line depends: it is attached to two of the four horizontal tubes on which the Y frames are fastened. $cd$ is the pipe fastened to the end of the rod; the end of this pipe has a screw, which passes through a nut, and acts against the end of the lever $d$, whose centre of motion is $g$, and whose other extremity is $f$, where there is a small piece of hard steel with a notch, for the reception of the plumb-line $fb$, suspended from $g$. Against the upper surface of the arm $gd$, a helical spring continually presses downwards; it is fastened above the end of the lever, at $e$; by which means, the arm $gd$ is constantly pressed against the end of the pipe, obviating the possibility of any play or shake of the lever, round its centre $g$. The same figure contains an elevation of the frame-work just described, as seen by an eye in the plane of the diaphragm produced. It is necessary that it should be closely inspected, for the purpose of obtaining an adequate idea of its construction. In this figure, $xv$ is a small cylinder, with a screw and loose collar at the end $v$, for fastening the plumb-line, which goes over the notch $n$, and passes through a hole in the upper part of the axis at $f$, and out again at $b$, almost touching the mother-of-pearl at $p$. $sr$ is a strong spring, fixed at $s$, through the middle of which, at $r$, passes a screw, which is, in fact, an adjusting screw, for bringing the plumb-line close to the dot on the surface of the diaphragm; and here it is necessary to observe, that the plane of the divided arch and that of this diaphragm, are one and the same when produced. There is no part of the instrument more complete than the apparatus for suspending the plumb-line, and that which regards the dot. I shall now return to a farther consideration of the construction of the axis. In Plate XII. there is also a horizontal view of the upper part of the axis; A being the head of the microscope, and B the little diagonal speculum, for throwing the light on the diaphragm. C is the opening in the axis above the object-glass; and D a brass slider, for covering the opening at C. E and F are two pulleys, attached to the side of the axis, over which pass two strings, having their ends united in opposite points of the shutter D; the other two ends of the string being within reach of the observer, who by this means easily opens or shuts the slider. In Plate XIV. ABCD is the moveable frame, fastened to the top of the external stand, and having an octagonal opening at E, for receiving the brass work connected with the four horizontal pipes carrying the Ys. The touching points between the octagon and cylinder, are g, b, n, at which parts of the frame hard pieces of metal are inserted. To prevent all possibility of shake in the cylinder, which would render an adjustment of the instrument troublesome, if not impossible, there are two strong screws at m and n. One is a helix, which acts against m, and against the end of the sliding piece n; so that, by a condensation of the helix by the screw m, the piece n acts against the head of the cylinder inserted in E. Plate XI. represents an elevation of the instrument seen sideways, and is that part to which the long microscope is attached: it serves to show the formation of the interior stand carrying the sectorial tube. ABCDEF are mahogany uprights, firmly united at the bottom and sides by proper cross pieces, and at top by the plate of metal abcd, through the ends of which pass those of four horizontal pipes, the plate abcd being one which carries a Y, hidden in this elevation, by the upper part of the head of the microscope. In the middle of the cross pieces, which unite the side of the frame to its corresponding one, are two wheels with long axles, as before mentioned. In this elevation they are seen at B and E; and have strings passing from them to their respective sides of the tube, where they attach to the pins P, P. At the ends of the axles nearest to this elevated side are two other pulleys. In the view which this plate affords, these wheels are projected against the others just spoken of; but their uses will be more readily understood, on perceiving the strings which pass over the upper pulleys, and afterwards sustain the weights W, W, in their upright cases. In this elevation is seen the telescope attached to the side of the great tube: it is used when the instrument is got into the plane of the meridian. The vessel for receiving the plummet is seen at V; and at S the adjusting-screw, for elevating or depressing the frame which supports it. LL is the clamp-arch, supposed to be attached to the other side of the tube, or that which supports the lamp. At the bottom of the stand is seen the azimuth circle, and the apparatus belonging to it. For the purpose of conveying a clear idea of the arrangement of the lower pulleys, and the manner in which the two arches are joined to each other at the end of the telescope, there is given, in Plate XII. a horizontal view of the same. The vessel for receiving the plummet, its supporting frame, and the magnifier for viewing the dots or points on the divided limb, are likewise represented. The body of the telescope is here taken away, leaving nothing more than the plate at its end, with the contiguous work belonging to the wires. To show with distinctness and sufficient perspicuity, the manner in which the cross wires are sustained in the tube, also the means by which they are adjusted, figures are given in Plate XII. These also show the micrometer-screw, and the mode of clamping it to the proper arch. In the horizontal representation of the end of the telescope, the wires are seen in the centre, and also the two screws, with the helical spring for adjusting and retaining them. EF is a strong brass arch, with an edge bar IK; placed parallel to the divided arch. At EF are seen two milled-headed screws, passing through a metallic embracement of the bar and arch, which are firmly connected with the apparatus belonging to the micrometer by their means. At S is a piece of hard polished steel, against which the point of the micrometer-screw rests; and, as the arch EF is the segment of a circle whose radius is its distance from the axis of the sector, the point of that screw always buts against the steel head in the same place. In this plate is also seen a vertical section of the same parts. Here, EF is the back arch, and MS the micrometer-screw. This figure also shows the means by which the pieces carrying the wires, and inserted into the end of the telescope, are retained in their proper places. CA and DB are two long pillars, which pass through an annular piece of brass parallel to the end of the tube. A screw with a windlas-like head is seen at G, from the turning of which, the wires are moved in one of their proper directions. A screw for giving them a motion at right angles to that obtained by the fore-mentioned one at G, is seen in the horizontal view of the end of the telescope at H. It would be swelling this account to an inconvenient size, if I were to attempt any farther explanation of the plates; I shall, therefore, close this article with a few observations on the manner of adjusting the instrument for observation. **Manner of adjusting the Instrument for Observation.** The feet of the external stand should be first carefully brought into a horizontal plane; and, when they are so, the azimuth circle will be, necessarily, parallel to it, having its centre under the middle of the opening in the mahogany frame screwed on the top of the stand. This being done, and the instrument set up, the plane of the arch should be brought parallel to one of the sides of the stand, in which situation, the internal frame is to be clamped to the azimuth circle, and the wire brought to its proper distance from the limb, by means of the adjusting-screw attached to one of the sliders, which carries the concave receptacle and conical point. The dot at zero should then be brought exactly under the plumb-line, as seen through the magnifier, and the point on the micrometer-head, at which its index stands, noted. The instrument is then to be turned half round; and, if the same dot on the arch still continues bisected, it will afford a proof of the internal stand being upright in one direction. But, if the dot should not continue bisected by the plumb-line, it must be made to do so, and the revolutions, or parts of a revolution, counted; half of which is to be turned back on the micrometer-head. The same dot, zero, is then to be brought under the wire, (plumb-line,) by means of the other adjusting-screw beneath the azimuth circle. If the stand is pretty accurately set up, one operation is sufficient for bringing the interior frame upright in one direction, *viz.* either in that of the meridian, or the one at right angles to it. The arch is then to be turned round 90°, and the same operation gone through. This being properly done, the interior frame is made perfectly upright. The next step to be taken, is that of placing the long level on its axis above, and rectifying that axis by means of the Y plate screws. If this be done carefully, the bubble will remain between the pointers of the level, whatever position the sector may be placed in. Having thus rectified the instrument, by making the internal frame upright, and the axis horizontal, the only remaining point to engage attention is, placing the plumb-line at a proper distance from the arch: this is done by means of the screw acting on the spring just under its point of suspension. If great care be used in going through these several adjustments, the instrument may, at any future time, be accurately adjusted for observation, by turning the proper screw belonging to the azimuth circle, and bringing the arch to its usual distance from the wire. Laying off the Points, or dividing the Limb of the Sector. The first step preparatory to finding the length of the radius, was to mount the sector in its frame, and adjust the counterpoising weights. By attention to the proper points on the levers, the axis was kept from bending, the pivots not having more than a weight of two pounds to support. This done, a tool with a well defined point was made to press lightly against the face of the arch, and firmly sustained in that situation, while the sectorial tube was slowly moved to the right and left: a fine line was by this means described on the limb, passing through the centres of the golden pins. The arch having been thus struck, the telescope was taken out of its frame, and laid on the edge of a very strong plank, having its axis horizontal, and the pivots resting in Ys firmly fastened in the middle. The end of the arch, whose face became vertical, was supported by a brass plate screwed down on the end of the plank. When the pivots were placed in the Ys, and the telescope sustained in several places, to keep it from bending, a brass slider, on the surface of the plank, was moved till the line before mentioned coincided with that described on the arch. The telescope was then quickly taken out of the Ys, and, as speedily as possible, brought into a similar position on the other side; for which purpose, braces to support the tube had been previously prepared. By these means, twice the length of the radius was obtained; proper care having been taken to have the Ys so placed, that the centre of the pivots should be in the same plane with the two sliders at the extremities of the plank. The distance between the lines was then measured, and $\frac{1}{16}$ taken for the chord of $7^\circ 10'$, which was immediately laid off on the face of the sector, on both sides zero. Although little doubt could be entertained of the truth of the total arc thus assumed, yet, that the length of its chord might be compared with that derived from the usual modes of operation, Mr. Berge (as proposed by Mr. Ramsden) prepared a brass arch, which he let into a frame, on which, after striking a portion of a circle with the radius obtained as above, he laid off the chord of $60^\circ$. This arch he divided by continual bisection, till he obtained the chord of $7^\circ 10'$, which he compared with the same angle laid off on the sector's limb. He had the satisfaction of finding no perceivable difference; and, that there really existed none, was denoted by the unresisted fall of the points into their respective holes. The arch of the sector was then divided into degrees, and every degree into five minutes; and the holes were afterwards opened with a tool made for the purpose. As gold pins had been let into the arch, Mr. Berge was enabled to go through the division of it with great success, and afterwards to enlarge the holes, without destroying his accurate work. The observations will offer a more satisfactory testimony of the credit due to his abilities as a workman, than any opinion which I might express myself as entertaining, although founded on the same data. It remains for me only to observe, that I think he has delivered this instrument into my hands without any imperfection of execution; and that I believe it would not have been superior, had the ingenious inventor lived to complete it. Adjustment of the meridional and horizontal Wires. After the arch was divided, the axis of the telescope was laid on a pair of Ys connected to a firm support, and made nearly horizontal. The tube was then brought up to a level with the axis, and sustained at proper intervals, whilst the end of the telescope rested on a small piece of metal connected to a fixed bar, by means of an adjusting-screw. This end was then moved, till an object sufficiently small, (a speck or dot,) at a proper distance, appeared nearly in the centre of the field. The telescope was then properly secured from bending, and rendered perfectly steady, but admitting of a small motion sideways, the Ys having also a corresponding adjustment. A microscope, furnished with a moveable wire, was then fastened to a beam attached to the brick wall, and its end brought close to the edge of the arch of the telescope. Upon this edge, as well as on that of the other arch, Mr. Berge had the address to lay off a point, very nearly in that place where the plane passing through the axis and zero cuts the arches. This being done, the telescope and Ys were moved laterally, till the vertical wire bisected the speck. The system of wires was then turned, till the meridional one was made exactly perpendicular to the axis, as seen from the mark being bisected in every part of the wire, when the end of the telescope was moved up and down by the adjusting-screw. The axis was then carefully taken out of the Ys, and inverted: it was afterwards placed as before, and the distance between the spot and vertical wire estimated by the eye. The telescope was then moved in azimuth, half that quantity, and the meridional wire brought to a bisection on the speck. Repeating this operation twice or thrice, the vertical wire became accurately perpendicular to the line passing through the centre of the conical axis, and also in the plane passing through the centre of the tube. The next step was, to move the whole system of wires in the direction of the perpendicular, in order that the horizontal one (at right angles to the vertical wire by construction) should be also brought into its proper position. For this purpose, the telescope was moved a little in azimuth, and the proper wire made to bisect it accurately, at which time, the wire of the micrometer before mentioned was brought over the dot on the edge of the limb. In this position of things, the instrument was taken off the Ys, and turned over; it was then again carefully placed in its former position, and the end of the telescope brought up by the adjusting-screw, till the distant speck was bisected by the horizontal wire. Now, if this horizontal wire had been, by accident, placed so that the point of intersection of the two wires was exactly in the true centre of the telescope, the dot on the edge of the other limb would have been bisected by the wire of the anterior microscope. This was found not to be the case; but it was made to be so, by halving the differences, and moving the horizontal wire so as to bisect the mark. After this had been again examined, the vertical wire was examined, when it was found necessary to go through a part of the operation a second time. This was to be expected; but the wires were, by these means, at last properly placed, and guards were then fixed over their adjusting-screws. I shall now proceed to speak of the use I made of this sector in the year 1802. Particulars relating to the Operations of the Year 1802. I have already stated, that a proper observatory had been provided for the reception of the zenith sector. The dimensions of it were twelve feet square at bottom, and six feet square at top; its proportions being the same as those of the external stand. A floor having a square vacuity, to admit of the instrument standing on the ground, covered the joists of it. The sides of the observatory were of strong painted canvas; and the roof of wood, with an aperture, which could be opened or closed at pleasure, for viewing the stars near the zenith. The instrument, with this observatory, was erected in the Tower on the 3d of April, merely to examine all its parts, and to ascertain whether any thing could be done to render it more perfect. Some trifling addenda were accordingly made, and the whole, thus rendered perfect, was removed to the Royal Observatory, and erected in the garden of the Astronomer Royal, close to the eastern extremity of the transit room. I am now to specify, that my intentions were to devote, from this period, the whole or the greatest part of the following summer, to the use of this sector; nor did I indeed imagine such a portion of time more than sufficient. I purposed to erect it at Dunnose, and at Clifton, the extremities of my arc; and also at Arbury Hill, near Daventry, the station almost in the middle of it. This last station I fixed upon, because it was proper to ascertain how far the observations for determining the extent of the whole arc, would agree with any others made for finding the value of its parts. The erecting of it at Greenwich was necessary, for the purpose of observing the zenith distances of certain stars, which were afterwards to be observed at Dunnose, thereby affording means of ascertaining the latitude of that station. The instrument remained at the Royal Observatory till the 26th of April; and, although the weather was for most part of the time unfavourable, yet the erecting of it there will be found, as appears in a future part of this work, to have answered the proposed end. One very material service accrued to myself; this was, the advice and instruction I received from the Astronomer Royal, for the successful management of the sector, by which I scrupulously governed myself throughout the whole of the subsequent campaign. Having observed the zenith distances of some few stars, and made myself completely master of every adjustment about the instrument, the sector, with all its apparatus, was sent to the Isle of Wight, by way of Southampton; every possible care being used to protect it from injury, not only while transporting by land, but also when under the act of being taken into, and removed out of, the vessel which conveyed it from that place to Cowes. It will be readily supposed, that watchfulness and care were necessary, to preserve this complicated instrument from being damaged by accident or roughness of the roads. In the year 1794, an iron cannon was sunk in the ground, for the purpose of permanently preserving the point on Dunnose, where the direction of the meridian was observed in 1793. It must be now remarked, that the cannon so inserted could not have its breech placed so low as might have been wished; in consequence of which, it became necessary to erect the observatory for the reception of the sector some little distance southward of the old station. The distance from the centre of the gun to the point over which the instrument was afterwards erected, was six feet and a half. To procure for the external stand, and thence for the whole apparatus, a firm foundation, I caused four long stakes to be driven into the ground, one for each foot of the stand, to which its feet were firmly screwed down. The surfaces of the stakes were then cut off smooth, and brought into the same horizontal plane, by which means, the interior frame and sector were placed much within the limits of their several adjustments. The pointed top of Sir Richard Worsley's obelisk afforded me an excellent means for bringing, with the assistance of the side telescope and azimuth circle, the plane of the arch into the true meridian. The distance and magnitude of that object is extremely convenient for the purpose. Its bearing from the meridian of the station is $87^\circ 42' 33''$, as I shall show in its proper place. The side telescope was turned to this object very frequently; and I never found the vernier, on the azimuth circle, to indicate any serious warp in the stand. Its greatest variation was $4'$; but, for several days together, it did not amount to $30''$. The weight of the plummet, I adjusted to the strength of the plumb-line, in the usual way. I suspended it in air, and gradually increased its weight, till the wire broke. This plummet was then immersed in the vessel appropriated for its reception. It will, perhaps, not be improper to observe, that I was careful to give the plummet its maximum of weight, that its wire might not be subject to motion from streams of air. As it was to be apprehended that errors would result, from the effects of an inequality of temperature in the air within the observatory, I placed two thermometers, both adjusted to a third; near the telescope. One I elevated as high as the axis, the other I laid on the hollow brass cylinders which connect the divided arch with that behind it, usually called the back arch. In the day, I found (as may be seen in the register of observations) the heat a little greater at the top of the tent than towards the bottom; and the reverse was generally the case at night. To equalize the temperature at those times when the sun shone out, or the weather was hot, I opened the shutters in the roof, as well as the door of the observatory, a considerable time before the moment of observation. By these means, the air within the tent was rendered tolerably uniform in its degrees of heat. For the space of a week following the commencement of my observations, I suspended a third thermometer from the milled-headed key which turns the diaphragm placed inside the telescope. As the situation of this thermometer was midway between the two others just mentioned, I always found the temperature there, a mean between those degrees shown by the upper and under thermometers; and as, in the course of the time specified, I had various opportunities of satisfying myself on this point, I desisted from making any farther use of it. For the purpose of ascertaining the limits of the errors likely to result from the cause now spoken of, it will be right to institute some little inquiry into its mode of operation. In Plate XVI. Fig. 1, let CD be the line passing through the centre of the sectorial tube, brought into any position for observation; the angle made with the zenith being ACB, and CA the consequent direction of the plumb-line. CB and BA may therefore represent the radius and arch of the sector, when in a state of uniform temperature throughout. Now, at any time, let the thermometer at the top C, indicate a degree of heat superior to that shewn by the other at B; and let it also be supposed, that the difference between those degrees of heat, at any intermediate point, is directly as the distance of that point from C or B; and farther, let the tube CB be extended to D, while the arch AB continues of the same length. If the line CA be extended to F, and the line AE be drawn parallel to BD, meeting the arch FD in E, then will the small space FE measure the error in the observed zenith distance of the star. As the angle ACB must in all cases be small, ACB and EF may be considered as two similar sectors of circles; under which supposition, we get $FE = \frac{AB \cdot EA}{CB}$; and, applying this to an extreme case occurring at Arbury Hill, on the 12th of September, we get $AE = \frac{5^\circ \times 0.0001237 \text{ inches} \times CB}{2 \times 12}$, hence $FE = \frac{5^\circ \times 0.0001237 \times 60.26'}{2 \times 12} = 0''.596$. As few of the stars selected for observation were, at either of the stations, so far from the zenith as $6^\circ$, it is obvious little inaccuracy can have resulted from the difference of temperature here spoken of; and this supposition will receive farther support, from the actually near approach of the two temperatures to an equality with each other, as appears by taking the mean results of the last two columns in the register of observations. That the scrupulous mind may be satisfied in this particular, I shall insert, in its proper place, a table for supplying the correction arising from this cause; as the effect of a greater heat in the upper part of the tent is an error in excess, so a reverse of the case produces one in defect. On the first convenient opportunity, I measured, with great care, the distances between every successive set of dots on the divided arch, contained between zero and $7^\circ 10'$. This was done at a time when the thermometers denoted a perfect uniformity in the temperature of the air within the tent, and when, from the calmness of the day, no streams of air could affect the plumb-line. Although I had, previously to the performance of this matter, perfectly satisfied myself that the rays of heat, emitted from the lamp illuminating the face of the arch, do not expand it perceptibly, yet I thought it best to wait for a day when the strength of the light should enable me to discover, and properly bisect, the points, without the aid of that lamp. Between zero and $7^\circ 10'$, on the left hand arch, I found there were 430 revolutions of the micrometer-screw + 38.2 divisions; and, between the same point and $7^\circ 10'$ on the right hand, 430 revolutions + 39.2 divisions. From this it appears, that the mean value of one revolution of the screw, is $0'59''098$. Mr. Berge endeavoured to place the arch, carrying the apparatus of the micrometer, so that one revolution of the screw should be exactly a minute. On trial, he found it nearly a second short; for which reason, he divided the head into 59 parts, and called each of them a second. I think it proper to repeat the observation, that the two arches were measured with the greatest care, because it admits of the remark, that every space subtending $5'$ was measured with the same part of the screw, beginning very nearly from 9 on the index. This instrument will, at a future period, probably pass into other hands; it may therefore be right to state, that I found, from an examination of the screw, an error of nearly $1''$, in the part contained between 17 and 19 on the index, arising from a small notch which, with a magnifier, I could plainly perceive on one of the threads. As it cannot but be the general wish to have some evidence of the accuracy with which this sector has been divided, and also how far I have succeeded in the performance of what is now under consideration, a table will be given, in which the value of every $5'$, in the first degree on each side zero, will be found in revolutions and parts of the screw. Having towards the end of June found my observations sufficiently numerous, and apparently sufficiently accurate, from the regular differences subsisting amongst them, I took down the sector, and, with every thing belonging to it, repaired to Clifton, the northern extremity of my arch. The instrument arrived there in safety, on the 20th of July; and, as the direction of the meridian had been previously determined, the instrument was immediately set up, and made ready for use. At this station, Laughton spire afforded me an excellent mark for adjusting the instrument in the plane of the meridian. The bearing of it is $1^\circ 56' 12''$ south-west; and, from my being able to see it in the observatory, without rolling up either of its canvas sides, I had ready means, at all times, of turning the telescope to that object. And I can take upon me to say, that during the whole of my stay at this station, I never found the instrument out of the plane of the meridian more than half a minute. Of the 27 stars observed at Dunnose, 17 were observed at this station; they were the following, viz. $\beta$, $\gamma$, $45d$, $46c$, $51$, $16$, $\mu$, Draconis; $1\kappa$, $10\nu$, Cygni; $\eta$, $\xi$, Ursae; $22\tau$, $85\nu$, $52$, $\upsilon$, Herculis; $\alpha$ Persei, and Capella. As the weather for most part of the time proved favourable, the observations were completed on the 22d of July; and, as there appeared to be sufficient time, between that period and the arrival of the season which would necessarily terminate my operations, to carry on my meridional line to the Tees mouth, I reconnoitered the country in that quarter, and selected the stations all the way between it and Clifton. On the 23d of July, the instrument and observatory were taken down, and the large theodolite erected over the point. White lights were sent to the distant stations, and were all observed, except those fired on the 30th day of the same month; and, as the night on which those lights were burnt was remarkably clear, and it was therefore probable that some intervening land obscured the distant hill, I desisted from making any farther attempt towards the execution of the above scheme, as any greater loss of time might prevent me from making the proposed observations on Arbury Hill. I therefore sent the sector to this last-mentioned place, where it arrived on the 3d of September, and was erected on the 7th, the direction of the meridian having been previously ascertained, by two double azimuths of the pole star. But it is proper I should observe, that the sector was not set up over the old station, as injury to some amount would have been sustained by the person farming the soil, owing to its cultivated state. The spot on which I fixed, was 34 feet to the north, and 28 towards the west, of the former station. Of the stars seen at Clifton, 12 were observed at Arbury Hill. These observations were continued, with very little interruption, till the 4th of October, when the party, with all the apparatus, returned to London; the zenith sector being found as perfect on its return as when first sent into the field, a circumstance inferring both the strength and perfect union of its parts. Particulars relating to the Measurement of a new Base Line, on Misterton Carr, in the Year 1801. The apparatus used for the measurement of this base, was the same as that employed on Hounslow Heath, Salisbury Plain, and Sedgemoor; and the like pains were taken to ensure its accuracy, as were used on those occasions. The points for lining out the base were put into the ground with great truth and precision; the large theodolite being used as one of the means, and in the same way as in measuring the base on Salisbury plain. Previous to the commencement of this operation, two large blocks of oak, with square holes on their upper surfaces, were sunk in the ground, at the extremities of the base; the point of intersection of the diagonals of each hole, severally denoting them. These diagonals were drawn on lead, cast into the holes, and ground to a smooth plane, even with the surface of the block. Before the measurement began, the working chain A, and the 50-feet chain, were both compared with the standard B. For this purpose, a calm cloudy day was waited for, which opportunity presented itself on the 2d of June. The pickets for the registered heads were then driven into the ground a considerable depth, and the coffers laid in a right line between them. The chain A was then laid out perfectly straight; and five thermometers, equally distant from each other, were put close to its side, their temperatures being as follows. **Thermometers.** 1 — 2 — 3 — 4 — 5. 67° 65° 67°,5 — 67°,5 — 67°,5. The chain A was then taken out of the coffers, and B laid out in its stead. The difference of their lengths, which was measured with the micrometer-screw, was found to be 1 revolution 6 divisions, viz. A longer than B; the temperature remaining constant the whole time of trial. In the course of the day, the same operation was repeated, the five thermometers standing at 69°,5 — 69° — 69°,5 — 69° — 69°, when B was found to be 1 revolution 6½ divisions of the micrometer-head shorter than A. Therefore, the mean, viz. 1 revolution 6¼ divisions, was considered as the true difference of their lengths. The length of twice the 50-feet chain was, at this trial, found to exceed that of B, 2 revolutions 4¾ divisions; which is nearly the same determination as formerly resulted, from a comparison of the chains with each other on Sedgemoor. It may be seen too, by referring to the account of the measurement of the base on that spot, that the difference between the lengths of the standard B and common chain A, was nearly the same at that period as now; the difference being 1 revolution 7 divisions. I therefore concluded I might, with safety, suppose the length of the standard chain B to be exactly the same then, as at the period when Mr. Ramsden compared it with the points inserted into the cast iron bar, mentioned in the first account of the trigonometrical operations. The measurement of this, the fourth base, commenced on the 6th of June; and was continued, without much interruption from bad weather or other causes, till the 28th of July, when it concluded with the 263d chain, the overplus, 38,321 feet, being carefully determined, by means of a silver wire and pointed plummet let fall over the point marking the north-west extremity of the base. The two chains were then carefully compared with each other; when it was found, that the wear of the chain A was exactly one division on the micrometer-head, or $\frac{1}{260}$ part of an inch. As the length of this base is nearly the same as that on Sedgemoor, it was reasonable to suppose that the elongation of the chain, by the working of the joints in each measurement, would be found the same, provided no injury had taken place from accidental circumstances, or rusting of the pivots and holes, during the time the chains were laid up in the Tower. After the reduction of the base, I shall have occasion to show that my ideas were correct in this point, as Mr. Berge has lately remeasured both chains. Angles of the great Triangles observed in the Years 1800, 1801. At Beacon Hill. | Between | Mean | |---------|------| | The north and south end of base | $20^\circ 47' 19''$ | | | $20^\circ 25'$ | | | $19.75''$ | of an Arc of the Meridian. | Between | Mean | |---------|------| | North end of Base and Gringley | 34° 44' 40.75" | | | 42.25" | | | 42.25" | | | 43.25" | | Gringley and south end of Base | 13° 57' 22.75" | | | 24" | | | 24.25" | | | 25" | | Heathersedge and Gringley | 13° 8' 15.5" | | | 16" | | | 17.5" | At North End of Base. | Beacon Hill and south end of Base | 60° 17' 16" | | | 16.25" | | | 17.25" | | Beacon Hill and Gringley | 74° 46' 55.5" | | | 56.25" | | | 57.25" | | | 58" | At South End of Base. | Beacon Hill and north end of Base | 98° 55' 26" | | | 27" | | | 28" | | | 29" | | Beacon Hill and Gringley | 114° 51' 31.5" | | | 31.75" | | | 32.5" | | | 32.75" | | | 33.75" | At Gringley. | Beacon Hill and south end of base | 51° 11' 5.25" | | | 5.75" | | | 6.75" | | | 7.25" | | | 7.5" | MDCCCIII. Between Beacon Hill and north end of Base - 70 28 21,5 21,75 22,5 23,25 Beacon Hill and Heathersedge - 23 10 5 6 7 Sutton Ashfield and Heathersedge - 46 20 23,5 24,5 At Heathersedge. Beacon Hill and Gringley - - 80 4° 37,75 38,5 39,25 Sutton Ashfield and Gringley - - 54 52 36,5 37,5 38,5 Orpit and Sutton Ashfield - - 39 8 37,25 37,75 38,25 39,5 39,75 At Sutton Ashfield. Heathersedge and Gringley - - 78 47 1,25 2,25 2,5 Orpit and Heathersedge - - 60 22 24,5 25,5 26,5 Hollan Hill and Orpit - - 113 49 8 9 10 ### At Orpit. | Location | Degrees | Minutes | Seconds | Mean | |---------------------------------|---------|---------|---------|------| | Heathersedge and Sutton Ashfield | 80 | 28 | 56.25 | 57.25| | Hollan Hill and Sutton Ashfield | 21 | 27 | 19.5 | 20.5 | | Bardon Hill and Hollan Hill | 62 | 8 | 24.5 | 25 | | Castle Ring and Bardon Hill | 56 | 3 | 13.75 | 14.75| ### At Hollan Hill. | Location | Degrees | Minutes | Seconds | Mean | |---------------------------------|---------|---------|---------|------| | Sutton Ashfield and Orpit | 44 | 43 | 30.75 | 32 | | Bardon Hill and Orpit | 74 | 52 | 36.25 | 38 | ### At Bardon Hill. | Location | Degrees | Minutes | Seconds | Mean | |---------------------------------|---------|---------|---------|------| | Hollan Hill and Orpit | 42 | 58 | 58.75 | 59.5 | | Castle Ring and Orpit | 68 | 24 | 3.75 | 4.75 | | Corley and Arbury Hill | 38 | 25 | 12.5 | 13.25| An Account of the Measurement At Castle Ring. Between Bardon Hill and Orpit | Mean | |------| | 55 32 43 | | 43,25 | | 43,75 | | 44,25 | | 44,75 | | 45 | Corley and Bardon Hill | Mean | |------| | 47 54 40,5 | | 41,75 | | 42,5 | | 43,25 | | 43,5 | At Corley. Castle Ring and Bardon Hill | Mean | |------| | 72 32 45,75 | | 46,25 | | 46,75 | | 47 | Arbury Hill and Bardon Hill | Mean | |------| | 107 20 13,5 | | 14,25 | | 15,75 | At Arbury Hill. Corley and Bardon Hill | Mean | |------| | 84 14 32,5 | | 33,25 | | 34,25 | Reduction of the Base to the Temperature of 62°. The apparent length of the base was 259 chains of 100 feet each, + 8 chains of 50 feet each, and the overplus of the last chain viz. 38,321 feet = 26338,321 Feet. The chain B, before the measurement, was found to be $1\frac{1}{4}$ divisions on the micrometer-head shorter. * For the observations of the angles of the triangles southward of Arbury Hill, see the Philosophical Transactions for 1795 and 1800. than A, the length of which, according to Mr. Ramsden's determination, may be taken = 100 feet + 0.1236 inches, in the temperature of 54°; which gives A 0.12363 parts of an inch too long. Therefore, if to this is added half the wear, viz. 0.00192 parts of an inch, we shall get $\frac{0.12555}{12}$, which $\times$ 259 gives 2,709 feet, which add The 50-feet chain, before the measurement, was compared also with B, and found to be 24 divisions on the micrometer-head longer; therefore, $\frac{0.0943}{12} \times 4$ = 0.0314 parts of a foot, which likewise add Again, the sum of all the degrees shown on the thermometers was 98083, wherefore, $\frac{98083}{5} - 54° \times 263.38 \times \frac{0.0075}{12} = 3.3713$ feet, is the correction for the mean heat in which the base was measured above 54°, the temperature in which the chains were laid off, and this also add Finally, for the reduction to the temperature of 62°, or 8° on the brass scale, we have $\frac{0.1237 \times 263.38 \times 8°}{12} = 1,720$ feet, which subtract Hence we have the true length of the base, in the temperature of 62°, = The surface of the ground on which this base was horizontally measured, is said to be not more than 35 feet above the surface of the sea, in the mouth of the Humber, at half tide. And, although it may not perhaps be a very correct deduction, yet, as I understand that conclusion arose out of a levelling operation, it may be taken for granted that we shall not err, as to sense, in our conclusions, if we consider Misterton Carr as situated on the mean surface of the spheroid. I shall, therefore, take 26342.7 feet for the true length of the base; and I think it cannot exceed or fall short of that quantity, more than two inches. Recent Comparisons of the standard and working Chains, with the points inserted in the cast Iron Bar. In the reduction of the foregoing base, I have taken it for granted, that the standard chain is precisely of the same length as when it first came out of the hands of Mr. Ramsden. Circumstances which need not be mentioned in this part of my paper, but which, in their proper places, will be explained, have induced me to get both the long chains remeasured. Mr. Berge, therefore, at my request, prepared the bar and plank, and lately went through the required operation. The particulars were as follow. The chain B was first measured in five successive removes, the first space of 20 feet having a thermometer in the middle of the bar, which stood at $48^\circ$; the second space or remove, having the same thermometer at $48^\circ,2$; the third, at $48^\circ,5$; the fourth, at $48^\circ,8$; and the 5th, at $48^\circ,8$; which gave the total length of the chain = 100 feet + 0.077 parts of an inch, in the mean temperature of $48^\circ,6$. The standard A was then measured in five successive removes; the thermometer at each remove being $48^\circ,5 — 48^\circ,6 — 48^\circ,7 — 48^\circ,8 — 48^\circ,8$; which gave the length of A = 100 feet + 0.132 parts of an inch, in the temperature $48^\circ,7$. From the Table of expansions in Vol. LXXV. of the Phil. Trans. the difference between the expansion of a rod of steel and one of cast iron, both of ten feet in length, is found to be \(0,00001\) part of an inch; therefore, the length of the chains, in the temperature of \(54^\circ\), agreeing with the points on the bar, will be \[A = 100 \text{ feet} + 0.1325 \text{ inches.}\] \[B = 100 \text{ feet} + 0.0778 \text{ inches.}\] In the Phil. Trans. for 1795, page 437, their lengths, in the same temperature, as deduced by Mr. Ramsden, are stated to be \[A = 100 \text{ feet} + 0.11425 \text{ inches.}\] \[B = 100 \text{ feet} + 0.05825 \text{ inches;} \text{ which gives a dif-}\] ference something less than \(\frac{2}{100}\) of inch between their present and former lengths. In the reduction of the preceding base, I have supposed the working chain A to be \(0.12363\) parts of an inch too long before the measurement began. If to this the whole wear be added, viz. \(0.00384\), we shall have the length of it, \(100 \text{ feet} + 0.1275\) parts of an inch; which differs only \(\frac{5}{1000}\) from the late deter- mination of Mr. Berge. **Calculation of the Sides of a Series of Triangles, extending from** **Dunnose, in the Isle of Wight, to Clifton, in Yorkshire.** Plate XV. In the former accounts of the trigonometrical operations it will be found, that triangles have been carried on from Dunnose to Arbury Hill. It will be proper to give them in this place, that the series may be complete, thereby superceding the ne- cessity of frequently referring to those papers. Butser Hill from Dunnose, 140580.4 feet. Phil. Trans. for 1795, p. 501. | No. of triangles | Names of stations | Observed angles | Diff. | Spherical excess | Error | Angles corrected for calculation | Distances | |------------------|-------------------|-----------------|------|-----------------|-------|---------------------------------|----------| | 1 | Butser Hill | 76° 12' 22" | -1.99| | | 76° 12' 21.5" | | | | Dean Hill | 48° 4' 32.25" | -1.54| | | 48° 4' 31.75" | | | | Dunnose | 55° 43' 7" | -1.53| | | 55° 43' 6.75" | | | | | 180° 0' 1.25" | 5.0 | -3.75 | | | | | | Dunnose from | { Butser Hill | | | | | 140580.4 | | | | { Dean Hill | | | | | | | | | { Dunnose | | | | | 183496.2 | | 11 | Dean Hill | 62° 22' 48.75" | -1.37| | | 62° 22' 47" | | | | Butser Hill | 48° 28' 41.5" | -1.23| | | 48° 28' 40" | | | | Highclere | 69° 8' 35" | -1.5 | | | 69° 8' 33" | | | | | 180° 0' 5.25" | 4.07 | +1.18 | | | | | | Dean Hill from | { Butser Hill | | | | | 156122.1 | | | | { Highclere | | | | | 125084.9 | | III | Butser Hill | 84° 31' 45.5" | -1.2 | | | 84° 31' 44.5" | | | | Hind Head | 66° 15' 54.5" | -0.83| | | 66° 15' 54.25" | | | | Highclere | 29° 12' 22" | -0.72| | | 29° 12' 21.25" | | | | | 180° 0' 2" | 2.7 | -0.7 | | | | | | Butser Hill from | { Hind Head | | | | | 78905.7 | | | | { Highclere | | | | | 148031.9 | | IV | Highclere | 34° 46' 15.75" | -0.81| | | 34° 46' 15" | | | | Hind Head | 83° 20' 14.25" | -1.36| | | 83° 20' 14" | | | | Bagshot Heath | 34° 46' 15.75" | -1.88| | | 01° 53' 31" | | | | | 180° 0' 1.75" | 3.09 | -1.34 | | | | | | Highclere from | { Bagshot Heath | | | | | 142952.6 | | | | { Hind Head | | | | | 160972.2 | | No. of triangles | Names of stations | Observed angles | Diff. | Spherical excess | Error | Angles corrected for calculation | Distances | |-----------------|------------------|----------------|------|-----------------|-------|--------------------------------|----------| | v. | Bagshot Heath | 55° 32' 26" | -0.89| | | 55° 32' 25.25" | | | | Highclere | 46° 10' 18.25" | -0.83| | | 46° 10' 17.75" | | | | Nuffield | 78° 17' 18.25" | -1.20| | | 78° 17' 17" | | | | | 180° 0' 2.5" | | | 2.94 | -0.43 | | | | | | | | | | | | | Nuffield from | Bagshot Heath | | | | | | | | | Highclere | | | | | | | | | | | | | | 105321.2 | | | | | | | | | 120374 | | vi. | White Horse Hill | 63° 7' 53.25" | -0.94| | | 63° 7' 53.5" | | | | Highclere | 63° 18' 16.75" | -0.94| | | 63° 18' 17" | | | | Nuffield | 53° 33' 49.5" | -0.86| | | 53° 33' 49.5" | | | | | 179° 59' 59.5" | | | 2.74 | -3.24 | | | | | | | | | | | | | White Horse Hill from | Nuffield | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | vii. | White Horse Hill | 38° 48' 13.25" | -0.67| | | 38° 48' 12.5" | | | | Nuffield | 86° 4' 16.25" | -1.21| | | 86° 4' 15" | | | | Brill | 55° 7' 33.5" | -0.71| | | 55° 7' 32.5" | | | | | 180° 0' 3" | | | 2.6 | +0.4 | | | | | | | | | | | | | Brill from | White Horse Hill | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | viii. | Brill | 50° 14' 44.5" | -1.18| | | 50° 14' 45" | | | | White Horse Hill | 64° 45' 43.75" | -1.34| | | 64° 45' 42.5" | | | | Stow on the Wold | 64° 59' 32" | -1.35| | | 64° 59' 32.5" | | | | | 180° 0' 0.25" | | | 3.88 | -3.63 | | | | | | | | | | | | | Stow from | White Horse Hill | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | ix. | Brill | 32° 34' 43" | -0.61| | | 32° 34' 42.25" | | | | Stow on the Wold | 60° 56' 6.25" | -0.64| | | 60° 56' 5.5" | | | | Epwell | 86° 29' 13.25" | -0.11| | | 86° 29' 12.25" | | | | | 180° 0' 2.75" | | | 2.37 | +0.38 | | | | | | | | | | | | | Epwell from | Stow | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | MDCCCLIII. 3 K | No. of triangles | Names of stations | Observed angles | Diff. | Spherical excess | Error | Angles corrected for calculation | Distances | |-----------------|------------------|----------------|------|-----------------|-------|---------------------------------|----------| | x. | Brill | 34° 23' 58.5" | -0.65" | " | " | 34° 23' 57.5" | | | | Epwell | 85° 0' 18.5" | -1.10" | " | " | 85° 0' 17.5" | | | | Arbury Hill | 60° 35' 45.5" | -0.70" | " | " | 60° 35' 45" | | | | | 180° 0' 22.5" | 2.46" | +0.04" | " | | | | | Arbury Hill from { Epwell | - | - | - | - | - | 83098.4 | | | Brill | | | | | | 146530 | | xi. | Arbury Hill | 89° 57' 4.5" | -1.14" | " | " | 89° 57' 5.5" | | | | Epwell | 54° 45' 18.75" | -0.57" | " | " | 54° 45' 18.25" | | | | Corley | 35° 17' 36.75" | -0.57" | " | " | 35° 17' 36.25" | | | | | 180° 0' 0" | 2.29" | -2.29" | " | | | | | Corley from { Arbury Hill | - | - | - | - | - | 117463 | | | Epwell | | | | | | 143827.8 | By the last triangle, the distance from Corley to Arbury Hill is 117463 feet, which distance, and all the others constituting the sides of this part of the series, are deduced from the base on Hounslow Heath, as well as that on Salisbury Plain. With regard to the triangles connecting the stations at Corley and Arbury Hill with the base recently measured in the north, it will be proper to let them rest partly on that base, and partly on the side Corley and Arbury Hill. And here I would remark, that in carrying on a series of triangles, whether for the purpose of a meridional measurement or otherwise, it is proper that a base of verification, answering at the same time as a new one of departure, should be measured every hundred miles at least. With this idea, therefore, the foregoing triangles, as well as those composing the remaining part of the series, should be furnished with three base lines, viz. one at each extremity, and the other in the middle. In calculating the sides, were the series thus circumstanced, it would be right to depend on each base for one third of the distance between it and the one next at hand, and use the mean result, as derived from the two adjoining bases, for the true lengths of the several sides within the other third. Thus, if two bases were found at the extremities of the arc in question, and one in the middle, as about Brill, the computation should be carried on, from the extreme bases, about one-sixth part of the meridional distance; and, from the middle base, one-third of the intermediate distance on each side; the remaining two arcs being determined from the respective base lines. That I may avoid prolixity, or the appearance of it, I shall compute the sides of the triangles northward of the two stations before mentioned, from the base measured on Misterton Carr only, and use the mean distances calculated on the above principle, when I find the total length of my arc. **Length of the Base on Misterton Carr, 26342.7 Feet.** | No. of triangles | Names of stations | Observed angles | Diff. | Spherical excess | Error | Angles corrected for calculation | Distances | |------------------|------------------|----------------|------|-----------------|-------|---------------------------------|----------| | xii. | Beacon Hill | 20° 47' 19.75" | " | " | " | 20° 47' 20" | | | | North end of Base| 60° 17' 16.5" | " | " | " | 60° 17' 13" | | | | South end of Base| 98° 55' 27.5" | " | " | " | 98° 55' 27" | | | | | 180° 0' 3.75" | " | " | " | | | | | Beacon Hill from | North end of Base | - | - | - | 64461.7 | | | | | South end of Base | - | - | - | 73321.9 | | | xiii. | Beacon Hill | 34° 44' 42.25" | " | " | " | 34° 44' 42" | | | | North end of Base| 74° 46' 56.5" | " | " | " | 74° 46' 56" | | | | Gringley on the Hill | 70° 28' 22.25" | " | " | " | 70° 28' 22" | | | | | 180° 0' 1" | " | " | " | | | | | Gringley from | North end of Base | - | - | - | 44338.2 | | | | | Beacon Hill | - | - | - | 75068.0 | | | No. of triangles | Names of stations | Observed angles | Diff. | Spherical excess | Error | Angles corrected for calculation | Distances | |-----------------|------------------|----------------|------|-----------------|-------|--------------------------------|----------| | xiv. | Beacon Hill | 13° 57' 24" | | | | 13° 57' 23" | | | | Gringley | 51° 11' 6.5" | | | | 51° 11' 5" | | | | South end of Base| 114° 51' 32.5" | | | | 114° 51' 32" | | | | | 180° 0' 3" | | | | | | | | Gringley from Beacon Hill | | | | | | 75068.2 | | | Wherefore the mean distance from Gringley to Beacon Hill is 75068.1 Feet. | | xv. | Heathersedge | 18° 40' 38.5" | +0.29| | | 18° 40' 38" | | | | Beacon Hill | 138° 9' 16" | -2.02| | | 138° 9' 16" | | | | Gringley | 23° 10' 6" | +0.65| | | 23° 10' 6" | | | | | 180° 0' 0.5" | | | | 1.08 | -0.58 | | | Heathersedge from Beacon Hill | | | | | | 92227.2 | | | Heathersedge from Gringley | | | | | | 156384.8 | | xvi. | Sutton Ashfield | 78° 47' 2" | -1.01| | | 78° 47' 1" | | | | Heathersedge | 54° 52' 37.5" | -0.24| | | 54° 52' 35" | | | | Gringley | 46° 20' 24" | -0.22| | | 46° 20' 24" | | | | | 180° 0' 3.5" | | | | 2.45 | +1.10 | | | Sutton Ashfield from Gringley | | | | | | 130399.7 | | | Sutton Ashfield from Heathersedge | | | | | | 115339.9 | | xvii. | Orpit | 80° 28' 57.25" | -0.85| | | 80° 28' 57" | | | | Heathersedge | 39° 8' 38.5" | -0.12| | | 39° 8' 38" | | | | Sutton Ashfield | 60° 22' 25.5" | -1.00| | | 60° 22' 25" | | | | | 180° 0' 1" | | | | 2.03 | -1.03 | | | Orpit from Heathersedge | | | | | | 101660.3 | | | Orpit from Sutton Ashfield | | | | | | 73826.6 | | No. of triangles | Names of stations | Observed angles | Diff. | Spherical excess | Error | Angles corrected for calculation | Distances | |-----------------|------------------|----------------|------|-----------------|-------|---------------------------------|----------| | XVIII. | Hollan Hill | 44° 43' 32" | -0.12| | | 44° 43' 31" | | | | Sutton Ashfield | 113° 49' 9" | -0.53| | | 113° 49' 7" | | | | Orpit | 21° 27' 20.5" | -0.18| | | 21° 27' 22" | | | | | 180° 0' 1.5" | | 0.73 | +0.77 | | | | | Hollan Hill from | Sutton Ashfield| | | | | 38375.2 | | | | Orpit | | | | | 95975.3 | | XIX. | Bardon Hill | 42° 58' 59.5" | -0.69| | | 42° 58' 59" | | | | Hollan Hill | 74° 52' 38" | -1.03| | | 74° 52' 37" | | | | Orpit | 62° 8' 25" | -1.01| | | 62° 8' 24" | | | | | 180° 0' 2.5" | | 2.75 | -0.20 | | | | | Bardon Hill from | Hollan Hill | | | | | 124454.7 | | | | Orpit | | | | | 135895.3 | | XX. | Castle Ring | 55° 32' 44" | -0.94| | | 55° 32' 43" | | | | Bardon Hill | 68° 24' 4.75" | -1.02| | | 68° 24' 3" | | | | Orpit | 56° 3' 14.75" | -0.90| | | 56° 3' 14" | | | | | 180° 0' 3.5" | | 2.85 | +0.65 | | | | | Castle Ring from | Orpit | | | | | 153235.2 | | | | Bardon Hill | | | | | 136717.8 | | XXI. | Corley | 72° 32' 46.5" | -1.19| | | 72° 32' 46" | | | | Castle Ring | 47° 54' 42.25" | -0.86| | | 47° 54' 42" | | | | Bardon Hill | 59° 32' 32.25" | -0.94| | | 59° 32' 32" | | | | | 180° 0' 1" | | 2.93 | -1.93 | | | | | Corley from | Bardon Hill | | | | | 106357.3 | | | | Castle Ring | | | | | 123539.7 | | XXII. | Arbury Hill | 34° 14' 33.5" | -0.98| | | 34° 14' 33" | | | | Corley | 107° 20' 14.25"| -1.99| | | 107° 20' 14" | | | | Bardon Hill | 38° 25' 13.25" | -0.80| | | 38° 25' 13" | | | | | 180° 0' 1" | | 3.37 | -2.37 | | | | | Arbury Hill from | Bardon Hill | | | | | 180426.0 | | | | Corley | | | | | 117457.8 | From the last triangle, we get $117457.1$ for the distance between Corley and Arbury Hill. By the xi. triangle, the distance between those stations is $117463$ feet; there is, therefore, a difference of nearly six feet between the two determinations; a quantity which cannot be considered unexpectedly great, as the side is more than twenty-two miles in length, and the whole series nearly two hundred miles long. If the computation had been carried on from Dunnose all the way up, the bases on Hounslow Heath and Salisbury Plain would have given the length of that on Misterton Carr about one foot greater than its measured extent. If the sides of the triangles contiguous to Corley and Arbury Hill be recomputed, from the mean distance between those stations, viz. $117460$ feet, no doubt whatever can be justly entertained of the general accuracy of the whole. These mean distances, as I have before observed, will be used in the calculations of the total length of the meridional arc. From the Base in the north, I have numbered the triangles downwards: the reason is obvious. **Calculation of the meridional Distance between Dunnose and Clifton.** To do this, it will be right to compare the distances of the several stations from the respective perpendiculars, both of Dunnose and Clifton, as derived from the observed direction of each meridian. In the Phil. Trans. for 1795 it will be seen, that the direction of the meridian was observed at the station on Dunnose, in 1793, the staff to which the pole star was referred being placed on Brading Down. The angle between that staff and the meridian, (see page 517 of that volume,) was found to be $21^\circ 14' 11''$.5, as derived from two double azimuths of the star, supported by several computed azimuths, applied to single but accurate observations. The angle between Butser Hill and the staff at Brading Down, was $0^\circ 15' 35''$,5. This, with the above angle, $21^\circ 14' 11''$,5, and particular angles of the series, gives, **The Bearings of certain Sides from the Parallels to the Meridian of Dunnose.** | Side | Bearing | |-----------------------------|------------------| | Dunnose and Butser Hill | $20^\circ 58' 39''$ NE | | Butser Hill and Highclere | $34^\circ 20' 17''$ NW | | Highclere and Nuffield | $35^\circ 30' 40''$ NE | | Nuffield and Brill | $4^\circ 51' 15''$ NW | | Brill and Arbury Hill | $12^\circ 30' 17''$ NW | | Arbury Hill and Bardon Hill | $7^\circ 42' 57''$ NW | | Bardon Hill and Orpit | $21^\circ 21' 9''$ NW | | Orpit and Heatersedge | $5^\circ 25' 52''$ NW | | Heatersedge and Beacon Hill | $61^\circ 52' 17''$ NE | These bearings, and the respective sides, give the following distances on the meridian of Dunnose, *viz.* | Side | Feet | Miles | |-----------------------------|--------------|----------| | Dunnose and Butser Hill | 131263.0 | 24.86 | | Butser Hill and Highclere | 122232.7 | 23.15 | | Highclere and Nuffield | 97984.7 | 18.56 | | Nuffield and Brill | 91755.3 | 17.38 | | Brill and Arbury Hill | 143054.1 | 27.09 | | Arbury Hill and Bardon Hill | 178792.4 | 33.86 | | Bardon Hill and Orpit | 126567.8 | 23.97 | | Orpit and Heatersedge | 101203.7 | 19.17 | | Heatersedge and Beacon Hill | 48480.7 | 8.23 | $1036334.4 = 196.27$, the distance between Clifton and the perpendicular to the meridian of Dunnose; which may be taken for the true length of the arc itself, as the distance of the former station from the meridian of the latter, is only 4770 feet. If the angle between the meridian and the staff at Brading Down was observed accurately, there can be no doubt of the correctness of this determination; but, as it was right on my part to adopt measures for bringing it to some proper test, I observed, as before stated, the direction of the meridian at Clifton. The particulars were as follows. **Observed Angles between the Pole Star, when at its greatest Elongations from the Meridian of Clifton, and the Staff erected over the Station at Gringley on the Hill.** **August, 1801.** | Days | Evenings | Mornings | |------|----------|---------| | 9th. | $100^\circ 45' 46''$ | | | 10th.| $100^\circ 45' 43.5''$ | | | 11th.| $100^\circ 45' 45.5''$ | $106^\circ 39' 34''$ | | 13th.| $100^\circ 45' 39''$ | $106^\circ 39' 22''$ | | 16th.| $100^\circ 45' 40.5''$ | | | 17th.| $100^\circ 45' 41''$ | $106^\circ 39' 24''$ | | 18th.| $100^\circ 45' 39''$ | $106^\circ 39' 28''$ | | 19th.| $100^\circ 45' 46.5''$ | $106^\circ 39' 27''$ | If a mean of all the evening observations be taken, we shall get $100^\circ 45' 42''.8$, for the angle between the staff at Gringley and the star when at its greatest eastern elongation from the meridian. In like manner, if a mean of all the morning observations be taken, we shall have $106^\circ 39' 27'$, for the angle between the same staff and the star on the western side. Hence, half their sum, $103^\circ 42' 35''$, nearly, will be the angle between Gringley and the meridian of Clifton; and its south-eastern bearing $76^\circ 17' 25''$. This, with certain angles of the series, gives the bearings of the following sides, viz. - Beacon Hill and Heathersedge - $61^\circ 51' 50''$ SW - Heathersedge and Orpit - $5^\circ 26' 19''$ SE - Orpit and Bardon Hill - $21^\circ 21' 36''$ SE - Bardon Hill and Arbury Hill - $7^\circ 43' 26''$ SE - Arbury Hill and Brill - $12^\circ 31' 0''$ SE - Brill and White Horse Hill - $50^\circ 15' 48''$ SW - White Horse Hill and Highclere - $27^\circ 48' 6''$ SE - Highclere and Butser Hill - $34^\circ 20' 49''$ SE - Butser Hill and Dunnose - $20^\circ 58' 9''$ SW. These bearings and sides give the following parallels to the meridian of Clifton. | Side | Feet | |-------------------------------|---------------| | Beacon Hill and Heathersedge | 43490.4 | | Heathersedge and Orpit | 101202.6 | | Orpit and Bardon | 126561.3 | | Bardon Hill and Arbury Hill | 178793.2 | | Arbury Hill and Brill | 143047.4 | | Brill and White Horse Hill | 93717.6 | | White Horse Hill and Highclere | 96031.4 | | Highclere and Butser Hill | 122219.8 | | Butser Hill and Dunnose | 131270.2 | The sum, $1036333.9$ feet, is the distance between Dunnose and the perpendicular to the meridian of Clifton; or, as observed with regard to the sum of the parallels to the meridian of the former, the length of the arc itself. MDCCCIII. There is, therefore, a difference of only half a foot, between the two results. We may, consequently, take 1036334 feet, for the distance required. I have observed, in a former part of this account, that the zenith sector was placed $6\frac{1}{2}$ feet from the station at Dunnose, and $3\frac{1}{2}$ feet from that at Clifton, the new points being due south of the old. We must therefore add 3 feet to 1036334; which gives 1036337 feet, for the total length of the arc of the meridian. The sum of the parallels to the meridian of Clifton, reaching down to Arbury Hill, is $45^\circ 047.5$ feet; and the distance of the latter from that meridian 1996 feet. This is, in fact, the meridional extent between the two old stations, as no correction is requisite. We must, however, subtract 30 feet from this distance, as the sector was put up $34\frac{1}{2}$ feet northward of the station on Arbury Hill. Therefore, $45^\circ 047.5 - 30 = 45^\circ 017.5$ feet, is the length of the arc comprized between the parallels of the new stations at Clifton and Arbury Hill: and, subtracting this from 1036337, we have 586319.5 feet, for the distance of this latter station from the point over which the sector was placed at Dunnose. Although the zenith sector was taken to the Royal Observatory at Greenwich, rather with a view of collecting materials for finding the latitude of Dunnose, than to answer any other purpose, yet, as I am provided with the means of finding the meridional distance between those places, and that with sufficient accuracy, I shall go through the work in this place. Distance between the Parallels of Latitude of Greenwich and Dunnose. In the Phil. Trans. for 1795, the station on Beachy Head is shown to be 269328 feet from the perpendicular at Greenwich, and 58548 from its meridian. In Plate XVI. Fig. 2, of this account, let DPB be a great spheroidal triangle on the earth's surface, P the pole, and DB the two stations at Dunnose and Beachy Head. Let also PGM be the meridian of Greenwich, [G,] and M the point where the parallel of Beachy Head to the perpendicular at G cuts that meridian. Then, from the above values of GM and BM, it will be found, that the latitude of B is $1''$,03 less than the latitude of M, and that too on any hypothesis of the earth's figure. Therefore, the distance in feet, between the parallels of B and G, is $269328 + 103 = 269431$. Now it has been shown, in the volume above referred to, (see page 522,) that the meridional distance between D and B is the mean of the two numbers 44258.6 and 44258.9 feet; and it must be remembered that, in deducing those conclusions, recourse was not had to matters of assumption, but to matters of fact, which were, the observed directions of the two meridians PD, PB, and the distance DB. Therefore, if 44259 feet be taken for the meridional distance between D and B, we shall have $269431 + 44259 = 313690$ feet, for the space between the parallels of latitude of Greenwich and Dunnose.* * In the Phil. Trans. for 1800, (see note to page 641,) in finding the value of the oblique arc between Black Down, in Dorsetshire, and Dunnose, I have used the expression $\frac{pm}{p+m-s,s^2} = d$; where $d$ is the length of the required degree, $p$ that of the great circle perpendicular to the meridian, $m$ that of the degree of the meridian itself, and $s$ the sine of the angle constituted by the oblique arc and the meridian. We have then found the total length of the whole meridional arc, and also the distances of two intermediate points from either, or from both, of its extremities. And, to bring the whole The demonstration of this rule I did not insert, on account of the previous length of the note alluded to; but I take this opportunity of supplying the omission, in the words of Mr. Dalby. Having the length of the degree on the meridian, and also that of the degree perpendicular to it, at the same point; to find the length of a degree in any other given direction, supposing the earth to be an ellipsoid. Let EP be one-fourth of the elliptic meridian; C the centre of the earth; CE, CP, the equatorial and polar semiaxes; G a given point on the meridian EP. Draw GR perpendicular to the meridian at G, meeting the axis PR in R; then RG is the radius of curvature of the ellipse, at the point G, which is perpendicular to the meridian at G. Conceive another ellipsoid FGSO to touch the given one in the point G. Then, it is evident, that if the curvature be respectively the same in the direction of the meridian and the perpendicular, on both ellipsoids at the point G, the curvature will also be equal on both figures, in any other direction at that point. And the like is manifest in spheroids of any other kind. Let M be the radius of curvature of the meridian at the point G; then, because RG is the radius of curvature in the perpendicular direction, if we take FS (at right angles to RG) = \(2\sqrt{RG \times M}\), and about FS, the axis to the semidiameter RG, describe the ellipsoid FGSO, it will be that having the curvature of G the same as on the other ellipsoid at that point. Let OGR be the plane of an ellipse, inclined to the meridian EGP, or to the plane FGS, in a given angle FRO, whose sine and cosine are s and c. Then, since RG, or rather its equal, is a semitransverse, in the plane FOSR, (which is perpendicular to RG,) to the semiconjugate RF, we shall have \(\frac{RG \times RF}{RG^2c^2 + RF^2s^2} = RO\), which, divided by RG, (RG being the semitransverse to RO in the perpendicular plane ROG,) gives \(\frac{RG \times RF}{RG^2c^2 + RF^2s^2}\) for the radius of curvature of the inclined ellipse OG at the point G. But, because the lengths of the degrees are proportional to their radii of curvature, if we put m and p for the meridional and perpendicular degrees, then RF or \(\sqrt{RG \times M}\) and RG may be expounded by \(\sqrt{pm}\), and p; hence, the expression will become \(\frac{pm}{p^2c^2 + m^2s^2}\), for the length under one point of view for future use, we shall have the following | Arcs | Feet | Miles | |-----------------------|----------|---------| | Clifton and Dunnose | 1036337 | 196.27 | | Dunnose and Arbury Hill | 586320 | 111.05 | | Dunnose and Greenwich | 313696 | 59.41 | | Clifton and Arbury Hill | 450017 | 85.23 | | Clifton and Greenwich | 722641 | 136.86 | | Arbury Hill and Greenwich | 272624 | 51.63 | Remark. In calculating the distance between the parallels of latitude of two places, connected by means of a trigonometrical operation, regard must be had to their difference in longitude. If the triangles run nearly north and south, in which case stations must lie both east and west of the two meridians, it is sufficiently correct to proceed on the supposition of the earth's surface being a plane; but if, on the contrary, the triangles wholly diverge from the two meridians, or even partly do so, first running off obliquely and then returning again, a different of the degree oblique to the meridian; or, putting \(1 - s^2\) for \(c^2\), and \(r\) for \(p - m\), it will be \(\frac{pm}{p - rs}\). Corol. If \(d\) be the length of the oblique degree, then, since \(d = \frac{pm}{pc + ms}\), we have \(p = \frac{s^2 dm}{m - c^2 d}\) and \(m = \frac{c^2 dp}{p - s^2 d}\). And, if \(D\) be put for the length of another oblique degree at the same point, and \(S\) and \(C\) the sine and cosine of its inclination to the meridian, we shall get \(m = \frac{S^2 c^2 - C^2 s^2}{S^2 D - s^2 d} \times D d\), and \(p = \frac{S^2 c^2 - C^2 s^2}{c^2 d - C^2 D} \times D d\), the meridional and perpendicular degrees, exhibited in terms of the oblique degrees combined with the sines and cosines of their inclinations to the meridian. Therefore, an ellipsoid may be determined from the lengths of two oblique degrees in the same latitude. We may likewise remark, from the nature of radii of curvature, at the same point \(G\), that the expression \(\frac{pm}{p - rs}\) will also give the oblique degree on different spheroids. method must be pursued. The necessity giving rise to this, originates from the radii of curvature of the oblique degrees continually varying, and the angles of convergency, between the several sides and their respective meridians, remaining unknown. It must be remembered, that the sides of the several triangles projected over the country, in this Survey, are not to be considered as so many distances on the earth's surface, but the lengths of the chord lines subtended by arcs. Therefore, it is manifest that, strictly speaking, all the chord angles should be used, and not the horizontal ones; with which, after the bearing of the first side with the meridian has been reduced to some plane beneath the earth's surface, a number of chord lines in the plane of that meridian are to be computed; the sum of which, augmented by the differences between those chords and their respective arcs, will give the true meridional distance. I have been at the trouble to calculate the distance between Clifton and Dunnose on this principle; and find the length of my arc to be 1036339.5 feet; which is, about $2\frac{1}{2}$ feet more than the distance determined by the other mode of computation. An advantage, however, attending a calculation on the principle now spoken of, is the ability of calculating, pretty nearly, the azimuth of any one station from an extremity of the arc. This, if the instrument with which the direction of the meridian is observed be not well divided, or otherwise not exactly fit for the operation, is necessary, and should be always done. The angle at Clifton, between Gringley on the Hill and the meridian, was observed to be $76^\circ 17' 25''$. According to my computation in the way spoken of, that angle is $76^\circ 17' 30''$. A difference of $5''$, working all the way up from Dunnose through an arc of $2^\circ 50'$, is as small as can be expected, and serves to prove that the angles of the triangles, as well as the observed direction of the meridians, are consistent. I have given the meridional distance between Clifton and Dunnose, bearings of the sides, &c. deduced from the most simple of the two methods; first, because the result is sufficiently accurate; secondly, because it places within general reach, the means of examining this part of my operation. In attending to this remark, it must be remembered, that a line from Dunnose perpendicular to the meridian of Clifton, is only 4853 feet. SECTION SECOND. Operations at the Station on Dunnose, the Southern Extremity of the Arc, with the Zenith Sector. May and June, 1802. On the 8th of May, the circular or large theodolite was placed over the point selected for a new station: its distance was $6\frac{1}{2}$ feet from the gun, and in a direction due south. The following objects were then observed, the readings of which, on the graduated limb, were as follows. | Object | Reading | |---------------------------------|------------------| | Sir R. Worsley's obelisk (the top) | $113^\circ 14' 28''$ | | East Cowes sea mark | $1^\circ 46' 36.5''$ | | Luttrell's Folly | $177^\circ 56' 25''$ | | Vane on the top of Portsmouth Church | $40^\circ 6' 44.5''$ | | Sir R. Worsley's obelisk, a second time | $113^\circ 14' 24.25''$ | The above objects were observed, in order that no possible mistake might result; as (though not probable) accidental circumstances might have given rise to a wrong statement of the bearing of some one of the number, (except Portsmouth Church,) in the account of 1795. Omitting the obelisk, the bearings of the other objects, as extracted from that Paper, will be as follows. LUTTRELL's Folly $23^\circ 0' 44''$ NW East Cowes sea mark $19 11 19$ NW Portsmouth Church $19 9 40$ NE If, from the readings on the limb, the angles between the obelisk and the other objects be taken, and applied to the last-mentioned bearings, we shall get the angle between the obelisk and the meridian, $87^\circ 42' 40''$ $\begin{array}{c} 35 \\ 45 \end{array}$ Mean, $87^\circ 42' 40''$. May 9th. Erected the observatory, drove four long stakes into the ground, and brought their several heads into the same horizontal plane. Then erected the stand, set up the sector, and adjusted the axis level, and the axis itself; determined the exact weight the plumb-line would bear, and then examined how much the cross wires were out of their proper positions, as follows. The stand being firmly screwed down to the stakes, the sector was turned on its axis, till the pointed top of Sir RICHARD WORSLEY's obelisk appeared in the field; it was then clamped to the azimuth circle, but subject to a small motion by turning an adjusting-screw. The pointed apex was then made to appear as just vanishing under the wires; in which situation of things, the side telescope was turned round, and laid in its several positions on the brass frame attached for its reception to the side of the sectorial tube; the top of the obelisk appearing as a vanishing point under the wires. On whichever face of its squares it was made to rest, the vernier of the azimuth circle read off to $84^\circ 5'$. The little telescope was then taken out of its frame, and the sector turned half round. It was then again introduced into its supports, and the interior stand moved, till the wires in the focus of the lateral telescope appeared on the obelisk as before. The vernier was then examined, which again stood at $84^\circ 5'$. This being settled, the sector was turned round, till its vernier stood at $176^\circ 22'$ on the azimuth circle, in which situation, the plane of the divided arc was necessarily parallel to that of the meridian. The task of observation then commenced, and the performance of it was as follows. **Observations made at Dunnose, to determine the Zenith Distance of β Draconis.** **Point on the Limb, 1° 50' North.** | Day of the month | Face of the arch, W. or E. | Plumb-line. | Observation of the star. | Zenith distance in revolutions and parts. | Zenith distance reduced. | Barometer. | Thermometer. | |------------------|---------------------------|-------------|--------------------------|------------------------------------------|-------------------------|------------|--------------| | May 11 | W | rev. div. | rev. div. | 9 17.9 | 1 50 0 13.08 | 1 49 46.90 | 28.85 | 43.5 | | 13 | E | 9 16.95 | 8 56.0 | | 19.95 | 40.02 | 28.85 | 36.5 | | 14 | W | 9 34.25 | 9 47.5 | | 13.25 | 46.73 | 28.92 | 34.5 | | 16 | E | 8 32.16 | 8 14.0 | | 18.16 | 41.81 | 28.82 | 35.5 | | June 5 | W | 6 23.00 | 6 30.0 | | 7.00 | 52.99 | 28.45 | 51.5 | | 8 | E | 8 14.02 | 8 2.0 | | 12.02 | 47.96 | 28.49 | 52.0 | | 11 | W | 6 57.40 | 7 2.6 | | 4.20 | 55.79 | 28.54 | 52.5 | | 13 | E | 9 39.50 | 9 29.5 | | 10.00 | 49.98 | 28.79 | 53.0 | | 14 | W | 8 19.29 | 8 23.7 | | 4.41 | 55.58 | 28.86 | 54.2 | | 16 | E | 3 56.61 | 3 47.0 | | 9.61 | 50.37 | 28.75 | 59.5 | | 17 | W | 8 38.52 | 8 41.5 | | 2.98 | 57.02 | 28.82 | 56.1 | | 18 | E | 11 31.87 | 11 21.5 | | 10.37 | 49.61 | 28.81 | 52.0 | | 20 | W | 8 53.27 | 8 54.2 | | 0.93 | 59.07 | 29.03 | 57.5 | | 21 | E | 10 27.05 | 10 19.7 | | 7.35 | 52.64 | 28.99 | 56.5 | MDCCCIII. An Account of the Measurement Observed Zenith Distances of γ Draconis. Point on the Limb, 0° 50' North. | Day of the month | Face of the arch, W. or E. | Plumb-line | Observation of the star | Zenith distance in revolutions and parts | Zenith distance reduced | Barometer | Thermometer | |------------------|---------------------------|------------|-------------------------|----------------------------------------|------------------------|----------|-------------| | May | | | | | | | | | 10 | E | 10 15:52 | 13 48:1 | 0 50 3 32:75 | 0 53 30:10 | 29:0 | — | | 11 | W | 9 38:66 | 5 56:4 | 41:26 | 38:62 | 28:85 | 43:9 | | 13 | E | 8 47:30 | 12 81:4 | 34:10 | 31:45 | 28:85 | 36:5 | | 14 | W | 7 32:38 | 3 49:2 | 42:18 | 39:54 | 28:92 | 34:5 | | 16 | E | 9 40:00 | 13 15:2 | 34:20 | 31:55 | 28:82 | 35:5 | | June | | | | | | | | | 11 | W | 7 20:70 | 3 29:5 | 50:20 | 47:58 | 28:34 | 53:5 | | 13 | E | 9 36:35 | 13 20:3 | 42:95 | 40:31 | 28:79 | 52:5 | | 14 | W | 8 25:26 | 4 33:4 | 50:86 | 48:24 | 28:26 | 54:3 | | 16 | E | 9 48:33 | 14 37:4 | 45:07 | 43:44 | 28:75 | 59:5 | | 17 | W | 8 32:66 | 4 39:4 | 52:26 | 49:64 | 28:82 | 56:0 | | 18 | E | 11 32:77 | 15 17:9 | 44:13 | 41:50 | 28:8 | 52:0 | | 20 | W | 8 9:48 | 4 17:0 | 51:48 | 48:86 | 29:97 | 58:6 | | 21 | E | 11 52:92 | 15 40:0 | 47:08 | 44:45 | 28:83 | 56:0 | Observed Zenith Distance of 45 d Draconis. Point on the Limb, 6° 15' North. | June | E | 9 27:76 | 10 53:1 | 6 15 1 25:34 | 6 16 24:48 | 28:8 | 49:5 | | 13 | W | 9 23:81 | 7 48:5 | 34:31 | 33:30 | 28:86 | 54:0 | | 14 | E | 10 18:90 | 11 46:5 | 27:60 | 26:74 | 28:77 | 59:0 | | 16 | W | 11 11:65 | 9 32:9 | 37:75 | 36:91 | 28:8 | 58:5 | | 18 | E | 8 18:20 | 9 46:7 | 28:50 | 27:64 | 28:97 | 56:0 | | 20 | W | 11 31:03 | 9 52:7 | 37:33 | 36:49 | 28:99 | 56:0 | | 21 | | | | | | | | Observed Zenith Distance of 46 c Draconis. Point on the Limb, 4° 40' North. | June | E | 9 34:85 | 12 46:0 | 4 40 3 11:15 | 4 43 8:46 | 28:8 | 49:5 | | 13 | W | 8 16:17 | 4 53:0 | 20:17 | 17:50 | 28:86 | 51:7 | | 14 | E | 13 15:62 | 16 27:0 | 11:38 | 8:69 | 28:77 | 59:0 | | 16 | W | 11 10:40 | 7 41:3 | 18:10 | 15:42 | 28:8 | 52:7 | | 18 | E | 8 32:10 | 11 47:0 | 14:90 | 12:22 | 28:97 | 58:4 | | 20 | W | 11 5:13 | 7 43:1 | 21:03 | 18:36 | 28:99 | 56:0 | | 21 | | | | | | | | ### Observed Zenith Distance of 51 Draconis. **Point on the Limb, 2° 25' North.** | Day of the month | Face of the arch, W. or E. | Plumb-line. | Observation of the star | Zenith distance in revolutions and parts | Zenith distance reduced | Barometer. | Thermometer. | |------------------|----------------------------|-------------|-------------------------|------------------------------------------|------------------------|-----------|--------------| | June 13 | E | 7 42,00 | 13 11,5 | 2 20 3 28,50 | 2 23 25,84 | 28,8 | Above | | | W | 8 10,63 | 4 33,3 | 36,33 | 33,68 | 28,9 | Below | | 16 | E | 9 0,00 | 12 23,8 | 28,80 | 26,14 | 28,8 | | | 18 | W | 10 48,27 | 7 11,5 | 36,77 | 34,12 | 28,8 | | | 20 | E | 8 47,43 | 12 21,0 | 32,57 | 29,92 | 29,0 | | | 21 | W | 11 2,23 | 7 24,5 | 36,75 | 34,08 | 29,0 | | ### Observed Zenith Distance of μ Draconis. **Point on the Limb, 4° 5' North.** | May 11 | W | 9 18,20 | 7 31,6 | 4 5 1 45,60 | 4 6 44,73 | 28,85 | 43,5 | | | E | 13 3,04 | 11 39,0 | 46,01 | 35,17 | 28,85 | 40,5 | | 13 | W | 10 2,03 | 8 18,4 | 42,63 | 41,80 | 28,92 | 36,3 | | 14 | E | 8 12,56 | 9 57,1 | 44,54 | 43,71 | 28,51 | 51,5 | | 13 | E | 9 29,34 | 11 15,8 | 45,40 | 44,63 | 28,79 | 53,5 | | 14 | W | 8 29,56 | 6 34,7 | 53,86 | 53,05 | 28,86 | 53,5 | | 16 | E | 4 9,66 | 5 50,0 | 46,34 | 45,51 | 28,75 | 59,5 | | 17 | W | 8 45,33 | 6 50,5 | 53,83 | 53,02 | 28,82 | 56,0 | | 18 | E | 11 44,3 | 13 34,0 | 48,17 | 47,35 | 28,80 | 52,0 | | 20 | W | 8 44,96 | 6 47,0 | 54,96 | 54,15 | 29,0 | 58,2 | | 21 | E | 10 34,60 | 12 25,0 | 49,40 | 48,58 | 28,99 | 55,8 | ### Observed Zenith Distance of 16 Draconis. **Point on the Limb, 2° 40' North.** | May 11 | W | 10 2,08 | 7 43,0 | 2 40 2 18,08 | 2 42 16,30 | 28,85 | 43,5 | | | W | 10 27,15 | 8 9,0 | 18,15 | 16,37 | 29,92 | 30,5 | | 14 | W | 8 31,87 | 6 14,0 | 17,87 | 16,09 | 28,82 | 39,9 | | 16 | W | 9 38,25 | 7 11,5 | 26,75 | 24,99 | 28,54 | 53,5 | | 13 | E | 4 28,90 | 1 48,3 | 39,60 | 37,86 | 28,86 | 52,0 | | 14 | W | 8 31,63 | 6 4,0 | 27,63 | 25,87 | 28,86 | 53,5 | | 16 | E | 3 51,90 | 6 14,5 | 21,60 | 19,83 | 28,78 | 61,0 | | 18 | E | 11 28,70 | 13 50,1 | 21,40 | 19,63 | 28,80 | 51,5 | | 20 | W | 8 25,61 | 5 55,2 | 29,41 | 27,65 | 28,95 | 57,7 | ### Observed Zenith Distance of 1 ν Cygni. Point on the Limb, 2° 20' North. | Day of the month | Face of the arch, W. or E. | Plumb-line. | Observation of the star. | Zenith distance in revolutions and parts. | Zenith distance reduced. | Barometer. | Thermometer. | |------------------|----------------------------|-------------|--------------------------|------------------------------------------|-------------------------|------------|--------------| | June 13 | E | rev. div. | rev. div. | 2 20 3 6.90 | 2 23 4.20 | Inches. | Above. Below. | | | W | | | | | | | | 14 | W | 9 26.60 | 12 33.5 | | | | | | 16 | E | 8 49.45 | 6 52.9 | | | | | | 18 | W | 10 12.05 | 6 58.8 | | | | | | 20 | E | 9 9.83 | 12 20.0 | | | | | | 21 | W | 11 1.83 | 7 44.2 | | | | | * Point on the limb 2° 25'. ### Observed Zenith Distance of 10 ν Cygni. Point on the Limb, 0° 40' North. | June 13 | E | 9 30.95 | 10 55.2 | 0 40 1 24.25 | 0 41 23.39 | 28.8 | 50.0 | | | W | 6 50.05 | 4 51.8 | 32.25 | 31.40 | 28.9 | 51.7 | | 16 | E | 8 43.00 | 10 9.5 | 25.50 | 24.64 | 28.8 | 60.0 | | 18 | W | 9 38.90 | 8 26.0 | 32.90 | 32.05 | 28.8 | 50.2 | | 20 | E | 8 30.78 | 10 0.0 | 28.22 | 27.36 | 29.1 | 55.0 | | 21 | W | 11 19.80 | 9 45.1 | 33.70 | 32.85 | 28.9 | 55.5 | ### Observed Zenith Distance of γ Ursæ. Point on the Limb, 4° 10' North. | May 9 | E | 11 42.53 | 12 14.6 | 4 10 0 31.07 | 4 10 31.12 | — | — | | | W | 8 34.32 | 7 54.4 | 38.92 | 38.98 | 28.8 | 50.5 | | 11 | E | 9 54.86 | 10 29.5 | 33.64 | 33.69 | 28.8 | 45.7 | | 14 | E | 10 1.47 | 10 34.5 | 33.03 | 33.08 | 28.9 | 38.5 | | 15 | W | 7 15.49 | 6 33.6 | 40.89 | 40.96 | 28.9 | 41.0 | | 17 | E | 8 54.00 | 9 29.5 | 34.50 | 34.56 | 28.8 | 46.0 | | 20 | E | 13 43.03 | 14 18.1 | 34.07 | 34.13 | 28.7 | 50.5 | | June 5 | W | 9 21.10 | 8 35.5 | 43.60 | 43.67 | 28.4 | 53.0 | | 8 | E | 8 58.90 | 9 36.2 | 37.30 | 37.36 | 28.5 | 55.5 | | 12 | E | 5 46.50 | 6 22.4 | 34.90 | 34.96 | 28.6 | 54.0 | | 13 | W | 10 40.70 | 9 56.4 | 43.30 | 43.37 | 28.7 | 59.1 | | 14 | W | 7 16.40 | 6 53.0 | 42.40 | 42.47 | 28.9 | 60.4 | | 16 | E | 9 3.20 | 9 41.1 | 38.00 | 38.06 | 28.8 | 72.0 | † Imperfect observation. † In page 417, 10 ν Cygni should be 10 ι, ξ Ursæ should be ξ, 85 ν Herculis should be 85 ι, and ν Herculis should be ν. ### Observed Zenith Distance of η Ursae. **Point on the Limb, 8° 15' South.** | Day of the month | Face of the arch, W. or E. | Plumb-line. | Observation of the star. | Zenith distance in revolutions and parts. | Zenith distance reduced. | Barometer. | Thermometer. | |------------------|----------------------------|-------------|--------------------------|------------------------------------------|-------------------------|-----------|--------------| | May 10 | E | rev. div. | rev. div. | o ' rev. div. | Inches. | | | | | E | 10 | 6,74 | 6 8,6 | 15 3 57,14 | 5 18 | 54,53 | | | E | 9 | 48,22 | 5 49,1 | 58,12 | 55,51 | 28,9 | | | W | 10 | 47,74 | 14 39,6 | 50,86 | 48,24 | 28,9 | | | E | 10 | 9,99 | 6 11,1 | 57,89 | 55,28 | 28,9 | | | W | 9 | 13,31 | 13 5,0 | 50,69 | 48,07 | 28,8 | | | E | 9 | 0,46 | 5 3,2 | 56,26 | 53,65 | 28,8 | | June 5 | W | 7 | 58,15 | 11 46,3 | 47,15 | 44,52 | 28,5 | | | E | 9 | 6,37 | 5 11,6 | 53,72 | 51,16 | 28,5 | | | W | 9 | 28,50 | 13 12,7 | 43,20 | 40,57 | 28,5 | | | E | 5 | 32,60 | 1 59,0 | 52,60 | 49,98 | 28,6 | | | W | 10 | 14,50 | 14 4,0 | 48,50 | 49,87 | 28,7 | | | E | 7 | 47,52 | 4 0,4 | 47,12 | 44,49 | 28,8 | | | W | 9 | 4,21 | 12 49,7 | 45,49 | 42,86 | 28,8 | | | E | 9 | 14,50 | 13 0,5 | 45,00 | 42,37 | 28,8 | | | W | 9 | 6,03 | 5 13,9 | 51,13 | 48,41 | 28,8 | | | E | 12 | 45,00 | 8 57,5 | 50,50 | 47,87 | 28,9 | * Doubtful. ### Observed Zenith Distance of ξ Ursae. **Point on the Limb, 5° 20' North.** | May 11 | W | 9 | 19,98 | 8 44,3 | 5 20 34,68 | 50 20 34,74 | 28,8 | 48,9 | 49,5 | | May 13 | E | 9 | 37,00 | 10 5,5 | 27,50 | 27,54 | 28,8 | 45,1 | 44,1 | | May 17 | E | 8 | 49,96 | 9 20,5 | 29,54 | 29,59 | 28,8 | 46,0 | 42,3 | | June 5 | W | 8 | 31,92 | 7 51,9 | 39,02 | 39,08 | 28,5 | 52,3 | 52,3 | | May 8 | E | 8 | 56,50 | 9 28,1 | 30,60 | 30,65 | 28,5 | 52,0 | 56,0 | | May 11 | W | 9 | 36,93 | 8 55,6 | 40,33 | 40,00 | 28,5 | 54,0 | 55,0 | | May 14 | E | 7 | 47,74 | 8 23,0 | 34,26 | 34,32 | 28,5 | 60,5 | 59,5 | | May 17 | W | 9 | 33,12 | 10 8,2 | 34,08 | 34,14 | 28,8 | 64,0 | 65,0 | | May 18 | W | 9 | 28,30 | 8 45,0 | 42,30 | 42,37 | 28,7 | 57,5 | 59,5 | | May 20 | E | 8 | 54,12 | 9 30,2 | 35,08 | 35,14 | 28,8 | 67,0 | 70,5 | ### Observed Zenith Distance of 85 i Herculis. **Point on the Limb, 4° 25' South.** | May 10 | E | 15 | 16,87 | 9 50,6 | 4 25 5 25,27 | 4 30 20,80 | 29,0 | 45,5 | 45,5 | | May 13 | E | 8 | 28,70 | 3 2,5 | 26,20 | 21,73 | 28,8 | 40,5 | 41,0 | | May 14 | W | 8 | 24,16 | 13 43,0 | 18,84 | 14,36 | 28,9 | 34,5 | 34,5 | | May 16 | E | 9 | 36,40 | 4 11,2 | 25,20 | 20,23 | 28,8 | 35,5 | 35,5 | | June 14 | W | 8 | 25,36 | 13 33,6 | 8,24 | 8,74 | 28,8 | 54,0 | 53,0 | ### Observed Zenith Distance of ν Herculis. **Point on the Limb, 4° 0' South.** | Day of the month | Face of the arch, W. or E. | Plumb-line. | Observation of the star. | Zenith distance in revolutions and parts. | Zenith distance reduced. | Barometer. | Thermometer. | |------------------|----------------------------|-------------|--------------------------|------------------------------------------|-------------------------|-----------|--------------| | May | | | | | | | | | 11 | W | 9 25.06 | rev. div. | 10 55.0 | 4 0 1 29.94 | 4 1 29.09 | 28.8 | | | E | 10 3.86 | rev. div. | 8 12.2 | 50.66 | 49.84 | 28.8 | | 13 | W | 9 44.22 | rev. div. | 11 27.6 | 42.38 | 41.55 | 28.9 | | | W | 2 56.33 | rev. div. | 4 40.3 | 42.97 | 42.14 | 22.8 | | June | W | 6 25.10 | rev. div. | 8 3.6 | 37.50 | 36.66 | 28.4 | | 5 | W | 9 26.10 | rev. div. | 11 21.0 | 53.90 | 53.09 | 28.5 | | | E | 9 58.25 | rev. div. | 8 17.0 | 41.25 | 40.42 | 28.8 | | 13 | W | 9 27.50 | rev. div. | 11 3.5 | 35.00 | 34.16 | 28.7 | | | E | 3 53.47 | rev. div. | 2 13.0 | 40.47 | 39.63 | 28.8 | | 16 | E | 11 42.00 | rev. div. | 13 23.0 | 40.00 | 39.17 | 28.8 | | | E | 9 34.90 | rev. div. | 7 53.4 | 40.50 | 39.66 | 28.9 | | 20 | | | | | | | | * Imperfect observation. ### Observed Zenith Distance of 52 Herculis. **Point on the Limb, 4° 15' South.** | Day of the month | Face of the arch, W. or E. | Plumb-line. | Observation of the star. | Zenith distance in revolutions and parts. | Zenith distance reduced. | Barometer. | Thermometer. | |------------------|----------------------------|-------------|--------------------------|------------------------------------------|-------------------------|-----------|--------------| | May | | | | | | | | | 13 | E | 9 52.55 | 7 32.0 | 4 15 2 20.55 | 4 17 18.78 | 28.8 | 40.5 | | | W | 10 16.56 | 12 30.4 | 13.84 | 12.06 | 23.92 | 34.5 | | 14 | E | 8 21.44 | 6 1.6 | 10.84 | 18.07 | 28.8 | 39.0 | | | W | 8 9.40 | 5 55.0 | 13.40 | 11.62 | 28.5 | 52.5 | | June | E | 9 29.24 | 11 34.5 | 5.26 | 3.46 | 28.5 | 53.5 | | 8 | W | 9 33.39 | 7 21.4 | 11.09 | 10.20 | 28.8 | 53.5 | | | E | 8 28.36 | 10 32.2 | 3.44 | 2.04 | 28.7 | 53.5 | | 13 | W | 8 8.60 | 6 56.5 | 11.11 | 9.32 | 28.8 | 59.5 | | | E | 8 57.87 | 11 4.0 | 5.13 | 3.33 | 28.8 | 57.5 | | 17 | W | 11 39.57 | 9 31.1 | 8.47 | 6.68 | 28.8 | 51.5 | | | E | 8 44.61 | 10 48.0 | 3.39 | 1.59 | 28.9 | 57.7 | | 20 | W | 10 7.00 | 7 56.4 | 9.60 | 7.81 | 28.9 | 59.5 | | | E | | | | | | | † Imperfect observation. ### Observed Zenith Distance of 22 τ Herculis. **Point on the Limb, 3° 45' South.** | Day of the month | Face of the arch, W. or E. | Plumb-line. | Observation of the star. | Zenith distance in revolutions and parts. | Zenith distance reduced. | Barometer. | Thermometer. | |------------------|---------------------------|-------------|--------------------------|------------------------------------------|-------------------------|------------|--------------| | May | | | | | | | | | 10 | E | rev. div. | rev. div. | 0° r.v. div. | 0° | Inches | Above | | | | 11 | 1,72 | 6 0,7 | 3 45 5 | 1,02 | 3 49 | | | | | | | | 56,51 | 29,0 | | | | | | | | | Below | | | | | | | | | | | 11 | W | 9 | 28,35 | 14 21,1 | 4 51,75 | | 48,23 | | | | | | | | | 28,8 | | | | | | | | | 43,5 | | | | | | | | | 43,5 | | 13 | E | 9 | 56,10 | 4 57,5 | 58,10 | | 54,59 | | | | | | | | | 28,8 | | | | | | | | | 40,5 | | | | | | | | | 41,0 | | 14 | W | 10 | 26,95 | 15 17,8 | 49,85 | | 46,32 | | | | | | | | | 29,9 | | | | | | | | | 36,5 | | | | | | | | | 38,5 | | 16 | W | 8 | 27,50 | 13 19,0 | 50,50 | | 46,98 | | | | | | | | | 23,8 | | | | | | | | | 39,0 | | | | | | | | | 39,9 | | June | W | 5 | 24,95 | 11 10,2 | 44,25 | | 40,72 | | | | | | | | | 28,4 | | | | | | | | | 50,5 | | | | | | | | | 51,0 | | 8 | E | 8 | 46,08 | 3 50,7 | 49,38 | | 45,85 | | | | | | | | | 28,5 | | | | | | | | | 50,5 | | | | | | | | | 52,5 | | 11 | W | 9 | 31,31 | 14 14,4 | 42,09 | | 38,55 | | | | | | | | | 28,5 | | | | | | | | | 53,5 | | | | | | | | | 52,0 | | 13 | E | 9 | 35,50 | 4 40,5 | 48,00 | | 44,47 | | | | | | | | | 28,8 | | | | | | | | | 52,0 | | | | | | | | | 51,5 | | 14 | W | 9 | 3,82 | 13 45,7 | 41,88 | | 38,34 | | | | | | | | | 28,8 | | | | | | | | | 53,5 | | | | | | | | | 54,0 | | 17 | W | 8 | 37,38 | 13 19,6 | 41,22 | | 37,68 | | | | | | | | | 28,8 | | | | | | | | | 57,5 | | | | | | | | | 58,0 | | 18 | E | 11 | 41,16 | 6 53,5 | 46,66 | | 43,11 | | | | | | | | | 28,8 | | | | | | | | | 51,5 | | | | | | | | | 52,7 | | 20 | W | 8 | 44,15 | 13 27,0 | 41,85 | | 38,31 | | | | | | | | | 28,9 | | | | | | | | | 57,7 | | | | | | | | | 58,5 | | 21 | E | 10 | 22,13 | 5 34,3 | 46,83 | | 43,30 | | | | | | | | | 29,0 | | | | | | | | | 59,5 | | | | | | | | | 57,6 | ### Observed Zenith Distance of Capella. **Point on the Limb, 4° 50' South.** | May | E | 10 | 37,73 | 10 29,0 | 4 50 0 | 8,73 | 4 50 | 8,74 | 28,9 | 64,0 | 65,1 | | | W | 9 | 16,65 | 9 18,2 | 1,55 | | 1,55 | | 28,7 | 63,5 | 66,0 | | | E | 9 | 42,06 | 9 34,4 | 7,66 | | 7,67 | | 28,8 | 57,4 | 54,9 | | | W | 8 | 38,83 | 8 39,4 | 0,57 | | 0,57 | | 28,7 | 53,0 | 58,1 | | June | W | 8 | 39,52 | 8 42,5 | 2,98 | | 2,98 | | 28,4 | 63,2 | 60,1 | | | E | 9 | 6,74 | 8 53,0 | 12,74 | | 10,54 | | 28,4 | 65,5 | 62,5 | | | W | 10 | 26,53 | 10 31,4 | 4,87 | | 4,88 | | 28,8 | 78,0 | 73,0 | | | E | 8 | 43,20 | 8 31,5 | 10,70 | | 10,73 | | 28,7 | 72,0 | 69,5 | | | W | 12 | 24,35 | 12 30,9 | 6,55 | | 6,56 | | 28,8 | 71,0 | 68,5 | | | W | 5 | 48,86 | 5 52,9 | 4,04 | | 4,05 | | 28,6 | 86,0 | 79,1 | --- **Operations at the Station near Clifton, the northern Extremity of the Arc, with the Zenith Sector. July and August, 1802.** On the 19th of July, the observatory and zenith sector were erected at the station, and the angle between the spindle of the weathercock on Laughton Spire and a staff at Gringley on the Hill, was observed on different arches of the large theodolite; the results being as follows, viz. $78^\circ 13' 32''$, $$\begin{array}{c} 34 \\ 35 \\ 32 \end{array} \quad \text{Mean } 78^\circ 13' 33''. $$ In a former article it has been shown, that Gringley is $76^\circ 17' 25''$ south-east of the meridian of Clifton; therefore, $78^\circ 13' 33'' - 76^\circ 17' 25'' = 1^\circ 56' 8''$, is the bearing of Laughton Spire from that meridian. The instrument, being otherwise adjusted for observation, was then brought into the plane of it, by setting off $1^\circ 56' 8''$ on the azimuth circle; the permanency of the line of collimation of the lateral telescope having been previously ascertained. **Observations made at Clifton, to determine the Zenith Distance of β Draconis.** **Point on the Limb, 1° o' South.** | Day of the month | Face of the arch, E. or W. | Plumb-line. | Observation of the star. | Zenith distance in revolutions and parts. | Zenith distance reduced. | Barometer. | Thermometer. | |------------------|---------------------------|-------------|--------------------------|------------------------------------------|-------------------------|------------|--------------| | July 20 | W | rev. div. | rev. div. | ° ' rev. div. | Inches. | | | | 22 | W | 12 1,04 | 12 14,8 | 1 0 13,76 | 1 0 13,78 | 28,8 | 58,0 | | 26 | E | 13 27,55 | 13 6,8 | 17,67 | 15,52 | 28,7 | 54,0 | | 28 | W | 9 21,94 | 9 32,3 | 10,36 | 10,38 | 28,8 | 59,5 | | 29 | E | 9 3,13 | 8 44,1 | 18,03 | 18,06 | 28,8 | 56,5 | | 31 | W | 9 34,59 | 9 44,1 | 9,51 | 9,52 | 29,0 | 57,2 | | Aug. 1 | E | 8 36,00 | 8 18,5 | 17,50 | 17,53 | 29,2 | 59,5 | | 3 | W | 8 57,87 | 9 8,9 | 10,03 | 10,05 | 29,16 | 68,0 | | 5 | E | 8 11,26 | 7 53,8 | 16,46 | 16,48 | 29,0 | 71,5 | | 7 | W | 8 51,74 | 9 1,6 | 8,86 | 8,87 | 28,9 | 67,2 | | 8 | E | 8 14,84 | 7 57,9 | 15,94 | 15,96 | 28,9 | 65,1 | | 12 | E | 11 7,98 | 10 50,6 | 16,38 | 16,41 | 29,15 | 58,1 | | 13 | W | 8 22,00 | 8 30,4 | 8,40 | 8,41 | 29,3 | 61,2 | | 17 | E | 8 30,33 | 8 15,8 | 14,53 | 14,55 | 29,1 | 70,5 | | 18 | W | 8 46,62 | 8 54,7 | 8,08 | 8,09 | 28,8 | 70,1 | Above. Below. ### Observed Zenith Distance of γ Draconis. **Point on the Limb, 1° 55' South.** | Day of the month | Face of the arch, E. or W. | Plumb-line | Observation of the star | Zenith distance in revolutions and parts | Zenith distance reduced | Barometer | Thermometer | |------------------|----------------------------|------------|-------------------------|------------------------------------------|------------------------|-----------|-------------| | July 20 | W | rev. div. | rev. div. | 0' rev. div. | Inches. | | | | | 11 49,24 | 13 12,8 | 1 55 1 22,56 | 1 56 21,69 | 28,9 | 56,5 | 55,0 | | 21 | E | 7 23,81 | 5 53,7 | 29,11 | 28,26 | 53,0 | 52,2 | | 22 | W | 7 54,31 | 9 17,1 | 21,79 | 20,92 | 54,5 | 54,5 | | 23 | E | 3 46,15 | 2 18,9 | 27,25 | 26,39 | 56,1 | 56,1 | | 26 | W | 9 8,47 | 10 29,5 | 21,03 | 20,16 | 64,0 | 64,0 | | 28 | E | 9 35,56 | 8 9,6 | 25,96 | 25,11 | 56,2 | 57,3 | | 29 | W | 8 44,41 | 10 4,5 | 19,09 | 19,03 | 56,5 | 56,5 | | Aug. 1 | W | 8 41,22 | 10 3,0 | 20,78 | 19,91 | 59,5 | 57,0 | | 3 | E | 9 7,59 | 7 40,3 | 26,29 | 25,43 | 68,0 | 64,5 | | 5 | E | 7 50,50 | 6 25,0 | 25,50 | 24,64 | 73,0 | 71,0 | | 7 | W | 9 7,55 | 10 24,6 | 17,05 | 16,18 | 64,2 | 65,2 | | 12 | E | 11 7,56 | 9 42,7 | 23,86 | 23,00 | 57,5 | 57,5 | | 13 | W | 8 12,48 | 9 29,4 | 16,92 | 16,04 | 63,0 | 61,2 | | 17 | E | 8 10,32 | 6 46,0 | 23,32 | 22,46 | 69,5 | 70,5 | | 18 | W | 8 32,97 | 9 48,5 | 15,53 | 14,65 | 70,0 | 70,1 | ### Observed Zenith Distance of 45 d Draconis. **Point on the Limb, 3° 25' North.** | July 22 | W | 7 35,91 | 6 10,5 | 3 25 1 25,41 | 3 25 24,56 | 28,7 | 54,0 | | 26 | W | 8 36,67 | 7 11,1 | 25,57 | 24,71 | 28,8 | 64,6 | | 29 | W | 8 53,36 | 7 26,6 | 26,86 | 26,02 | 28,8 | 56,5 | | 31 | E | 13 50,53 | 14 51,0 | 20,47 | 19,60 | 29,0 | 55,0 | | Aug. 7 | W | 8 47,50 | 7 18,6 | 28,90 | 28,04 | 28,9 | 65,0 | | 12 | E | 11 9,60 | 12 31,0 | 21,40 | 20,53 | 29,2 | 55,5 | | 13 | W | 8 10,99 | 6 38,9 | 31,09 | 30,24 | 29,3 | 60,1 | | 17 | E | 8 14,53 | 9 38,9 | 24,37 | 23,51 | 29,0 | 71,0 | | 18 | W | 8 15,03 | 6 41,3 | 32,73 | 31,88 | 28,8 | 68,0 | ### Observed Zenith Distance of 46 c Draconis. **Point on the Limb, 1° 55' North.** | Day of the month | Face of the arch, E. or W. | Plumb-line. | Observation of the star. | Zenith distance in revolutions and parts. | Zenith distance reduced. | Barometer. | Thermometer. | |------------------|----------------------------|-------------|--------------------------|------------------------------------------|-------------------------|-----------|--------------| | July 20 | W | 12 7,00 | 8 55,8 | 1 50 3 10,20 | 1 53 7,51 | 28,9 | 55,5 | | | | | | | | | | | | W | 7 28,12 | 9 21,4 | 1 55 1 52,28 | 8,53 | 28,7 | 54,0 | | | E | 9 29,68 | 7 31,3 | 57,38 | 3,43 | 28,8 | 57,2 | | | E | 9 29,77 | 7 31,7 | 57,07 | 7,74 | 29,0 | 55,3 | | Aug. 3 | E | 8 55,40 | 7 0,6 | 54,80 | 6,01 | 29,1 | 64,0 | | | E | 7 11,47 | 5 15,8 | 54,6 | 5,14 | 29,0 | 73,5 | | | W | 6 37,64 | 10 26,6 | 47,96 | 12,80 | 28,9 | 65,2 | | | E | 11 3,15 | 9 9,0 | 53,15 | 7,66 | 29,2 | 55,5 | | | W | 8 6,41 | 9 52,5 | 46,09 | 14,73 | 29,3 | 60,0 | | | E | 8 25,75 | 6 32,3 | 52,5 | 8,36 | 29,0 | 71,2 | | | W | 8 20,25 | 10 6,3 | 45,05 | 15,78 | 28,8 | 71,0 | ### Observed Zenith Distance of 51 Draconis. **Point on the Limb, 0° 20' South.** | July 28 | E | 9 31,75 | 7 50,7 | 0 20 1 40,05 | 0 29 29,21 | 28,8 | 55,0 | | | E | 9 29,90 | 7 48,5 | 45,0 | 3,56 | 29,0 | 55,0 | | Aug. 5 | E | 7 11,71 | 5 32,6 | 35,1 | 3,27 | 29,0 | 71,0 | | | W | 8 48,70 | 10 19,5 | 20,80 | 28,95 | 21,9 | 63,5 | | | W | 9 6,30 | 10 35,3 | | 23,15 | 28,9 | 66,5 | | | E | 11 7,00 | 9 30,5 | 35,5 | 34,66 | 29,2 | 55,5 | | | W | 8 1,71 | 9 29,5 | 27,79 | 26,13 | 29,3 | 60,2 | | | E | 8 27,62 | 6 52,0 | 34,2 | 33,77 | 29,0 | 70,1 | | | W | 8 20,96 | 9 47,4 | 26,44 | 25,58 | 28,8 | 67,0 | ### Observed Zenith Distance of μ Draconis. **Point on the Limb, 1° 15' North.** | July 20 | W | 11 51,87 | 20 9,3 | 1 15 1 42,57 | 1 16 41,73 | 28,9 | 58,0 | | | W | 9 11,90 | 7 20,9 | 44,00 | 43,17 | 28,8 | 58,2 | | | E | 9 11,32 | 10 11,0 | 39,63 | 38,84 | 28,8 | 56,5 | | | W | 9 55,53 | 8 40,0 | 45,53 | 44,70 | 28,8 | 59,0 | | Aug. 12 | E | 11 17,11 | 12 57,3 | 40,19 | 39,25 | 29,15 | 69,2 | | | W | 8 21,48 | 6 31,5 | 48,98 | 48,16 | 29,32 | 62,0 | ### Observed Zenith Distances of 16 Draconis. **Point on the Limb, 5° South.** | Day of the month | Face of the arch, E. or W. | Plumb-line | Observation of the star | Zenith distance in revolutions and parts | Zenith distance reduced | Barometer | Thermometer | |------------------|----------------------------|------------|-------------------------|------------------------------------------|------------------------|-----------|-------------| | July 29 | E | rev. div. | rev. div. | 9 26,41 | 6 31,7 | 2 53,71 | 53,99 | 28,8 | 59,7 | 59,5 | | Aug. 5 | E | 8 17,70 | 5 23,0 | | | 53,70 | 51,98 | 29,1 | 79,1 | 78,1 | ### Observed Zenith Distances of 1 x Cygni. **Point on the Limb, 2° North.** | July 20 | W | 13 45,26 | 15 42,5 | 0 25,1 56,24 | 0 26 55,43 | 28,9 | 56,5 | 55,0 | |-----------------|-----------------------------|------------|-------------------------|------------------------------------------|------------------------|-----------|-------------|-------------| | 22 | W | 9 12,66 | 11 10,3 | 56,64 | 55,83 | 28,7 | 54,0 | 54,0 | | 26 | W | 9 42,42 | 11 39,1 | 55,68 | 54,87 | 28,8 | 64,5 | 63,5 | | 28 | E | 9 29,47 | 7 27,2 | 2 2,27 | 27 0,47 | 28,8 | 55,2 | 55,2 | | 29 | W | 9 3,65 | 11 7,4 | 3,75 | 1,95 | 28,9 | 56,9 | 55,0 | | 30 | W | 9 43,53 | 11 37,3 | 1 52,77 | 26 51,95 | 28,7 | 57,0 | 55,0 | | 31 | E | 9 30,77 | 7 28,5 | 2 2,27 | 27 0,47 | 29,0 | 55,0 | 55,0 | | Aug. 5 | E | 7 8,34 | 5 9,1 | 1 58,24 | 20 57,43 | 29,0 | 71,2 | 69,2 | | 7 | W | 8 46,45 | 10 39,0 | 51,55 | 50,73 | 28,9 | 63,3 | 63,3 | | 9 | W | 8 32,50 | 10 24,6 | 51,10 | 50,28 | 28,9 | 66,0 | 65,0 | | 12 | E | 10 42,00 | 8 43,0 | 58,00 | 57,19 | 29,2 | 55,5 | 59,5 | | 13 | W | 8 1,11 | 9 50,9 | 49,79 | 48,97 | 29,3 | 60,0 | 59,0 | | 17 | E | 8 25,55 | 6 30,2 | 54,35 | 53,54 | 29,0 | 71,0 | 69,5 | | 18 | W | 8 27,85 | 10 17,0 | 48,15 | 47,33 | 28,8 | 66,0 | 66,0 | ### Observed Zenith Distances of 10 i Cygni. **Point on the Limb, 10° South.** | July 20 | W | 13 51,27 | 12 27,2 | 2 10 1 24,07 | 2 8 36,79 | 28,9 | 56,5 | 55,0 | |-----------------|-----------------------------|------------|-------------------------|------------------------------------------|------------------------|-----------|-------------|-------------| | 28 | E | 9 22,60 | 10 42,5 | 19,90 | 40,97 | 28,8 | 57,3 | 55,5 | | 29 | W | 9 8,23 | 7 38,5 | 28,73 | 32,12 | 28,8 | 56,7 | 56,5 | | 30 | W | 9 31,50 | 8 40 | 27,50 | 33,36 | 28,7 | 55,5 | 57,5 | | 31 | E | 9 19,20 | 10 39,5 | 20,30 | 40,57 | 29,0 | 55,0 | 55,2 | | Aug. 1 | W | 9 2,40 | 7 34,1 | 27,30 | 33,56 | 29,2 | 59,2 | 57,2 | | 5 | E | 7 0,70 | 8 23,2 | 22,50 | 38,36 | 29,0 | 68,5 | 68,5 | | 7 | W | 8 50,33 | 7 21,5 | 28,83 | 32,02 | 28,9 | 62,2 | 63,2 | | 9 | W | 8 47,48 | 7 18,0 | 29,48 | 31,37 | 28,9 | 65,5 | 66,5 | | 12 | E | 10 37,36 | 12 1,0 | 22,64 | 38,22 | 29,2 | 55,0 | 59,0 | | 17 | E | 8 21,50 | 9 47,0 | 25,50 | 35,36 | 29,0 | 61,9 | 68,9 | | 18 | W | 8 29,25 | 6 54,7 | 33,55 | 27,30 | 28,8 | 66,0 | 66,0 | An Account of the Measurement Observed Zenith Distance of γ Ursæ. Point on the Limb, 1° 20' North. | Day of the month | Face of the arch. E. or W. | Plumb-line. | Observation of the star. | Zenith distance in revolutions and parts. | Zenith distance reduced. | Barometer. | Thermometer. | |------------------|---------------------------|-------------|--------------------------|------------------------------------------|-------------------------|------------|--------------| | Aug. 17 | E | rev. div. | rev. div. | ° rev. div. | ° " | Inches. | Above. Below. | | | | | | | | | | | | | | | | | | | | | | | | | | | | Observed Zenith Distances of η Ursæ. Point on the Limb, 3° 5' South. | July 23 | W | 9 | 1,35 | 13 5 4 3,65 | 3 9 0,05 | 29,0 | 62,5 | | Aug. 26 | W | 9 | 26,00 | 13 30,9 | 4,90 | 1,30 | 28,9 | | Aug. 4 | W | 8 | 40,50 | 12 46,0 | 5,50 | 1,90 | 29,2 | | Aug. 8 | E | 7 | 34,74 | 3 22,0 | 17,74 | 9,15 | 29,0 | | Aug. 17 | E | 8 | 52,05 | 4 38,5 | 13,45 | 9,86 | 29,14 | | | | | | | | | | Observed Zenith Distances of ζ Ursæ. Point on the Limb, 2° 30' North. | July 29 | E | 9 | 8,82 | 9 21,5 | 2 30 0 12,68 | 2 30 12,70 | 28,8 | | Aug. 5 | W | 8 | 40,97 | 8 22,5 | 18,47 | 18,50 | 29,1 | | Aug. 8 | E | 8 | 25,15 | 8 37,0 | 11,83 | 11,87 | 29,0 | | Aug. 9 | W | 8 | 49,00 | 8 29,4 | 14,60 | 19,62 | 28,9 | | Aug. 17 | E | 9 | 10,43 | 9 22,0 | 11,57 | 11,59 | 29,4 | | | | | | | | | | Observed Zenith Distances of 85 i Herculis. Point on the Limb, 7° 20' South. | July 20 | W | 11 | 50,28 | 12 6,0 | 7 20 0 14,72 | 7 20 14,74 | 28,9 | | July 23 | E | 3 | 50,07 | 3 28,5 | 11,57 | 21,60 | 29,0 | | July 28 | W | 9 | 30,92 | 14 47,4 | 15 5 16,48 | 12,00 | 28,8 | | Aug. 3 | W | 10 | 15,40 | 10 26,5 | 20 0 11,10 | 11,12 | 29,0 | | Aug. 5 | E | 9 | 6,18 | 9 17,0 | 10,82 | 10,84 | 29,2 | | Aug. 5 | E | 8 | 2,52 | 7 42,0 | 19,52 | 19,75 | 29,0 | | Aug. 7 | W | 9 | 17,54 | 9 29,0 | 11,46 | 11,48 | 28,9 | | Aug. 17 | E | 8 | 15,52 | 7 56,0 | 18,52 | 18,55 | 29,0 | | | | | | | | | | ### Observed Zenith Distances of ν Herculis. **Point on the Limb, 6° 50' South.** | Day of the month | Face of the arch, E. or W. | Plumb-line. | Observation of the star. | Zenith distance in revolutions and parts. | Zenith distance reduced. | Barometer. | Thermometer. | |------------------|----------------------------|-------------|--------------------------|------------------------------------------|--------------------------|------------|--------------| | July 21 | E | rev. div. | rev. div. | 8 11,5 | 6 16,6 | 50 1 53,7 | 6 51 52,89 | 28,5 | 55,5 | 54,5 | | 29 | E | | | 9 14,1 | 7 17,0 | 56,1 | 55,29 | 28,8 | 60,7 | 61,5 | | 30 | W | | | 7 57,8 | 9 48,8 | 46,0 | 47,17 | 28,8 | 62,5 | 60,0 | ### Observed Zenith Distances of 52 Herculis. **Point on the Limb, 7° 5' South.** | July 28 | W | 8 58,72 | 11 15,5 | 7 5 2 15,78 | 7 7 14,00 | 28,8 | 58,5 | 58,5 | | 29 | E | 9 11,35 | 6 47,0 | 23,35 | 21,58 | 28,8 | 59,7 | 59,5 | | 30 | W | 10 1,29 | 12 16,0 | 14,71 | 12,93 | 28,8 | 61,0 | 59,0 | | Aug. 8 | E | 8 50,70 | 6 23,9 | 26,80 | 25,04 | 28,9 | 65,2 | 65,5 | ### Observed Zenith Distances of 22 τ Herculis. **Point on the Limb, 6° 40' South.** | July 29 | E | 3 56,30 | 3 57,9 | 6 40 0 | 1,60 | 6 39 59,40 | 28,8 | 60,7 | 61,5 | | 30 | W | 8 8,81 | 7 58,6 | 9,21 | 50,77 | 28,8 | 62,5 | 60,0 | | Aug. 1 | W | 8 5,20 | 7 53,1 | 11,10 | 48,88 | 29,2 | 67,0 | 67,0 | | 7 | W | 10 1,73 | 9 50,5 | 10,23 | 49,75 | 28,9 | 71,0 | 69,0 | | 12 | W | 10 16,30 | 10 4,0 | 12,50 | 47,48 | 29,2 | 65,2 | 63,3 | | 13 | E | 8 12,30 | 8 16,8 | 4,50 | 55,49 | 29,3 | 67,3 | 66,5 | ### Observed Zenith Distances of α Persei. **Point on the Limb, 4° 20' South.** | Aug. 8 | W | 9 7,66 | 7 45,7 | 4 20 1 20,96 | 4 18 39,91 | 28,9 | 66,5 | 63,0 | | 10 | W | 8 38,84 | 7 18,0 | 20,84 | 40,03 | 28,9 | 70,2 | 71,0 | | 13 | E | 10 27,76 | 11 45,6 | 17,84 | 43,03 | 29,3 | 57,0 | 54,0 | | 18 | E | 8 26,58 | 9 43,5 | 16,92 | 43,95 | 29,0 | 60,2 | 60,2 | | 19 | W | 8 11,42 | 6 47,5 | 22,92 | 37,94 | 28,8 | 60,5 | 60,3 | Observed Zenith Distances of Capella. Point on the Limb, 7° 40' South. | Day of the month | Face of the arch, E. or W. | Plumb-line. | Observation of the star. | Zenith distance in revolutions and parts. | Zenith distance reduced. | Barometer. | Thermometer. | |------------------|---------------------------|-------------|--------------------------|------------------------------------------|-------------------------|------------|--------------| | Aug. 7 | W | rev. div. | 9 7,20 | 9 36,0 | 7 40 0 28,80 | 7 40 22,85 | 28,7 | 66,0 | | | | | | | | | | | | Aug. 8 | E | rev. div. | 9 5,23 | 8 25,7 | 38,53 | 38,59 | 28,9 | 71,5 | | | | | | | | | | | | Aug. 9 | E | rev. div. | 6 28,62 | 5 48,0 | 39,62 | 39 68 | 28,9 | 81,5 | | | | | | | | | | | | Aug. 18 | W | rev. div. | 9 1,45 | 9 26,9 | 25,45 | 25,49 | 29,0 | 74,0 | | | | | | | | | | | | Aug. 19 | E | rev. div. | 8 3,80 | 7 28,0 | 34,80 | 34,86 | 28,8 | 68,7 | Operations at the new Station on Arbury Hill, near Daventry, with the Zenith Sector, in the Months of September and October, 1802. In the Phil. Trans. for 1800, page 658, it will be seen, that the bearing of the Summer House on Bardon Hill, in the north of Leicestershire, from the meridian of Arbury Hill, is 7° 37' 31" NW; and, as this spot is only 2776 feet westward from the meridian of Dunnose itself, it follows, that 7° 37' 31" may be taken for the bearing of the above object from Arbury Hill. To avoid, however, the possibility of any error arising from adopting this supposition, the direction of the meridian was ascertained, (before the zenith sector was got up,) by a double azimuth of the pole star. From this it appeared, that the angular point of the roof of a house about seven miles distant, was within a few seconds of the true northern direction; and also, that Bardon Hill (the summer house) was 7° 37' 35" north-west. By observing these two objects, as the weather suited, the sector was afterwards got into the plane of the meridian. Observations made on Arbury Hill, to determine the Zenith Distance of β Draconis. Point on the Limb, 0° 15' North. | Day of the month | Face of the arch, E. or W. | Plumb-line. | Observation of the star. | Zenith distance in revolutions and parts. | Zenith distance reduced. | Barometer. | Thermometer. | |------------------|---------------------------|-------------|--------------------------|------------------------------------------|--------------------------|------------|--------------| | Sept. 8 | W | 9 48,90 | 10 54,7 | 0 15 1 5,80 | 0 13 55,09 | 28,2 | 51,0 | | | | | | | | | | | | E | 9 37,98 | 3 20,5 | 11,48 | 49,40 | 28,8 | 70,5 | | | W | 9 17,78 | 10 23,0 | 5,22 | 55,67 | 28,8 | 71,5 | | | E | 9 16,33 | 8 6,5 | 9,83 | 51,06 | 28,8 | 68,2 | | | E | 9 26,17 | 8 16,0 | 10,17 | 50,71 | 28,8 | 79,3 | | | W | 8 21,00 | 9 25,0 | 4,00 | 56,89 | 28,9 | 76,5 | | | E | 9 7,68 | 7 57,0 | 9,68 | 51,21 | 28,9 | 71,0 | | | W | 9 29,13 | 10 34,0 | 4,87 | 56,02 | 29,1 | 74,5 | | | E | 9 4,27 | 7 51,8 | 11,47 | 49,41 | 29,0 | 64,5 | | | W | 10 43,25 | 11 48,7 | 5,45 | 55,45 | 29,0 | 65,5 | | | E | 9 27,65 | 8 17,3 | 10,35 | 50,53 | 29,1 | 79,0 | | | W | 9 25,82 | 10 30,7 | 4,88 | 56,04 | 29,0 | 64,0 | | Oct. 1 | E | 9 43,20 | 8 31,0 | 12,20 | 48,79 | 29,0 | 72,2 | | | W | 9 19,02 | 10 26,6 | 7,58 | 53,31 | 28,7 | 74,0 | Observed Zenith Distances of γ Draconis. Point on the Limb, 0° 40' South. | Sept. 10 | W | 8 53,85 | 11 6,4 | 40 2 11,55 | 0 42 9,76 | 28,2 | 51,5 | | | E | 8 47,75 | 6 31,9 | 15,85 | 14,07 | 28,53 | 48,2 | | | E | 9 46,65 | 7 28,7 | 17,95 | 16,17 | 28,8 | 70,3 | | | W | 9 18,90 | 11 31,5 | 12,60 | 10,82 | 28,8 | 67,5 | | | E | 9 1,78 | 6 42,8 | 17,98 | 16,20 | 28,8 | 68,3 | | | E | 9 16,52 | 6 58,2 | 17,32 | 15,54 | 28,8 | 79,8 | | | W | 8 9,97 | 10 20,5 | 10,53 | 8,74 | 28,8 | 67,5 | | | E | 9 16,97 | 7 0,8 | 16,17 | 14,39 | 28,9 | 70,5 | | | W | 9 16,00 | 11 27,6 | 11,60 | 9,81 | 29,1 | 74,0 | | | E | 9 10,47 | 11 23,0 | 12,53 | 10,75 | 29,0 | 59,5 | | | E | 9 17,50 | 7 0,8 | 16,70 | 14,92 | 29,1 | 64,0 | | | W | 9 21,63 | 11 33,5 | 11,87 | 10,08 | 29,9 | 64,0 | | Oct. 1 | E | 9 34,95 | 7 15,5 | 19,45 | 17,87 | 28,9 | 72,5 | | | E | 9 25,33 | 7 7,0 | 18,33 | 16,57 | 28,8 | 71,0 | | | W | 8 54,30 | 11 7,1 | 11,80 | 10,01 | 28,6 | 74,0 | ### Observed Zenith Distances of 45 d Draconis. **Point on the Limb, 4° 40' North.** | Day of the month | Face of the arch, E. or W. | Plumb-line. | Observation of the star. | Zenith distance in revolutions and parts. | Zenith distance reduced. | Barometer. | Thermometer. | |------------------|----------------------------|-------------|--------------------------|------------------------------------------|--------------------------|------------|--------------| | Sept. | | | | | | | | | 8 | W | 9 57,57 | 9 21,1 | 4 40 36,47 | 4 40 38,53 | 28,2 | 52,0 | | | | | | | | | | | 15 | W | 7 29,48 | 6 47,3 | 40,98 | 41,05 | 28,9 | 63,5 | | | | | | | | | | | 18 | E | 9 45,55 | 10 18,6 | 32,05 | 32,10 | 28,8 | 64,2 | | | | | | | | | | | 19 | W | 9 28,10 | 8 46,6 | 40,50 | 40,57 | 28,8 | 66,5 | | | | | | | | | | | 20 | E | 8 56,23 | 9 29,1 | 31,87 | 31,92 | 28,8 | 66,5 | | | | | | | | | | | 23 | W | 8 0,83 | 7 22,4 | 37,43 | 37,49 | 28,8 | 67,5 | | | | | | | | | | | 24 | E | 9 18,78 | 9 50,4 | 31,62 | 31,67 | 28,9 | 65,5 | | | | | | | | | | | 25 | W | 9 36,25 | 8 57,1 | 38,15 | 38,21 | 29,0 | 65,3 | | | | | | | | | | | 26 | E | 9 14,12 | 9 46,5 | 32,37 | 32,42 | 29,0 | 64,8 | | | | | | | | | | | 28 | E | 9 18,62 | 9 50,0 | 31,38 | 31,43 | 29,0 | 65,3 | | | | | | | | | | | 29 | W | 8 57,55 | 8 20,0 | 37,55 | 37,61 | 29,1 | 64,5 | | | | | | | | | | | 30 | W | 8 51,62 | 8 13,5 | 37,12 | 38,18 | 29,0 | 64,3 | | Oct. | | | | | | | | | 1 | E | 9 25,05 | 14 58,7 | 33,65 | 29,20 | 28,9 | 72,0 | | | | | | | | | | | 2 | E | 9 18,35 | 9 50,6 | 32,35 | 32,40 | 28,8 | 72,5 | ### Observed Zenith Distances of 46 c Draconis. **Point on the Limb, 3° 5' North.** | Sept. | E | 9 3,63 | 11 19,23 | 3 5 2 15,40 | 3 7 13,62 | 28,5 | 63,0 | 64,5 | |-------|-----|--------|----------|-------------|-----------|------|------|------| | | W | 9 37,3 | 11 19,4 | 15,67 | 13,89 | 28,2 | 51,0 | 54,0 | | | W | 9 30,08| 5 6,5 | 23,58 | 21,85 | 28,9 | 63,5 | 66,0 | | | W | 10 22,70| 7 55,9 | 24,80 | 23,04 | 29,0 | 61,5 | 65,5 | | | E | 9 29,12| 11 47,0 | 17,88 | 16,11 | 28,8 | 64,0 | 67,0 | | | W | 9 40,57| 7 16,3 | 24,27 | 22,51 | 28,8 | 66,5 | 72,0 | | | E | 8 34,27| 10 52,3 | 18,03 | 16,26 | 28,8 | 66,0 | 69,0 | | | W | 9 55,90| 7 29,0 | 26,90 | 25,14 | 28,8 | 66,5 | 69,5 | | | E | 8 2,67 | 11 20,4 | 17,73 | 15,95 | 28,8 | 79,2 | 75,3 | | | W | 9 20,01| 6 45,0 | 24,10 | 22,34 | 28,8 | 67,5 | 65,0 | | | E | 9 3,97 | 11 22,3 | 18,33 | 16,56 | 28,8 | 65,5 | 63,0 | | | W | 9 42,55| 7 19,2 | 23,35 | 21,58 | 29,0 | 65,5 | 67,3 | | | E | 9 9,10 | 11 27,0 | 17,90 | 16,12 | 29,0 | 64,5 | 66,5 | | | W | 9 17,52| 11 35,0 | 17,48 | 15,70 | 29,0 | 65,5 | 64,5 | | | W | 9 13,00| 7 48,4 | 23,60 | 21,83 | 29,0 | 64,5 | 69,0 | | | W | 9 4,20 | 6 38,8 | 24,40 | 22,64 | 29,1 | 64,5 | 69,5 | | Oct. | E | 9 18,65| 11 36,1 | 17,45 | 15,67 | 29,0 | 68,2 | 61,4 | | | E | 9 22,35| 14 41,1 | 18,75 | 16,97 | 28,8 | 68,0 | 70,5 | ### Observed Zenith Distances of 1κ Cygni. **Point on the Limb, 0° 45' North.** | Day of the month | Face of the arch, E. or W. | Plumb-line. | Observation of the star. | Zenith distance in revolutions and parts. | Zenith distance reduced. | Barometer. | Thermometer. | |------------------|---------------------------|-------------|--------------------------|------------------------------------------|--------------------------|------------|--------------| | Sept. | | | | | | | | | 7 | E | 8 12,72 | 10 25,2 | 0 45 2 12,48 | 0 47 10,69 | Inches. | 0 | | | W | 6 54,92 | 4 36,0 | 18,92 | 17,15 | 28 2 | 51,5 | | | | | | | | | 54,5 | | 15 | W | 8 52,42 | 8 31,5 | 20,92 | 19,15 | 28,9 | 62,5 | | | | | | | | | 65,3 | | 16 | W | 10 31,57 | 8 9,0 | 22,57 | 20,80 | 28 9 | 61,0 | | | | | | | | | 65,0 | | 18 | E | 8 21,80 | 10 38,0 | 16,20 | 14,42 | 28,8 | 64,3 | | | | | | | | | 67,5 | | 19 | W | 9 37,93 | 7 14,5 | 22,53 | 20,77 | 28,8 | 66,5 | | | | | | | | | 72,0 | | 20 | E | 8 24,05 | 15 43,6 | 40 7 19,55 | 13,27 | 28,8 | 65,0 | | | | | | | | | 67,0 | | 22 | E | 8 50,82 | 11 9,0 | 45 2 17,18 | 15,40 | 28,8 | 66,3 | | | | | | | | | 66,5 | | 23 | W | 8 56,10 | 6 33,5 | 22,60 | 20,83 | 28,8 | 67,5 | | | | | | | | | 65,3 | | 24 | E | 8 32,52 | 10 48,5 | 15,98 | 14,20 | 28,9 | 59,3 | | | | | | | | | 63,5 | | 25 | W | 9 44,57 | 7 23,5 | 21,07 | 19,30 | 29,0 | 66,5 | | | | | | | | | 67,0 | | 26 | E | 9 20,58 | 11 36,0 | 15,42 | 13,64 | 29,0 | 64,5 | | | | | | | | | 66,5 | | 28 | E | 9 31,90 | 11 47,7 | 15,80 | 14,02 | 29,0 | 60,5 | | | | | | | | | 62,5 | | 29 | W | 9 58,00 | 7 35,0 | 23,00 | 21,23 | 29,0 | 64,5 | | | | | | | | | 68,0 | | 30 | W | 9 48,10 | 7 24,9 | 23,20 | 21,43 | 29,0 | 62,0 | | | | | | | | | 65,5 | | Oct. | E | 9 9,42 | 11 26,0 | 16,58 | 14,80 | 28,9 | 64,0 | | | | | | | | | 66,5 | | | E | 9 21,82 | 11 38,0 | 16,18 | 14,40 | 28,0 | 65,0 | | | | | | | | | 68,0 | ### Observed Zenith Distances of 51 Draconis. **Point on the Limb, 0° 50' North.** | Sept. | E | 8 13,88 | 5 43,5 | 0 55 2 29,38 | 0 52 32,37 | 28,2 | 51,5 | | | W | 6 41,63 | 4 15,5 | 0 50 2 49,13 | 38,39 | 28,2 | 51,0 | | | | | | | | | 54,0 | | 10 | E | 9 16,00 | 11 53,7 | 37,70 | 35,96 | 28,2 | 51,0 | | | | | | | | | 54,0 | | 16 | W | 10 39,00 | 7 55,5 | 42,50 | 40,77 | 29,0 | 61,7 | | | | | | | | | 65,5 | | 18 | E | 8 42,00 | 11 19,7 | 36,70 | 34,96 | 28,8 | 64,0 | | | | | | | | | 67,2 | | 19 | W | 9 56,73 | 7 13,6 | 43,13 | 41,42 | 28,8 | 66,5 | | | | | | | | | 72,0 | | 20 | E | 8 26,10 | 11 13,0 | 35,90 | 34,15 | 28,8 | 66,5 | | | | | | | | | 69,5 | | 22 | E | 8 54,28 | 11 31,2 | 35,92 | 34,17 | 28,8 | 68,5 | | | | | | | | | 63,0 | | 23 | W | 9 4,53 | 6 21,9 | 41,63 | 39,89 | 28,8 | 67,5 | | | | | | | | | 65,5 | | 25 | W | 9 34,53 | 6 51,5 | 42,03 | 40,30 | 29,0 | 67,0 | | | | | | | | | 67,0 | | 26 | E | 9 24,17 | 12 1,4 | 36,23 | 34,49 | 29,0 | 59,5 | | | | | | | | | 64,5 | | 28 | E | 9 30,17 | 12 7,3 | 36,13 | 34,39 | 29,0 | 66,0 | | | | | | | | | 64,0 | | 29 | W | 9 17,85 | 6 53,9 | 40,95 | 39,21 | 29,0 | 65,5 | | | | | | | | | 69,5 | | 30 | W | 9 35,83 | 6 51,0 | 43,83 | 42,10 | 29,0 | 64,0 | | | | | | | | | 70,3 | | Oct. | E | 9 11,55 | 11 49,0 | 37,45 | 35,71 | 29,0 | 68,0 | | | | | | | | | 68,0 | | | E | 9 24,62 | 11 2,4 | 30,78 | 35,04 | 28,8 | 68,0 | | | | | | | | | 70,5 | MDCCCIII. ### Observed Zenith Distance of 10 Cygni. **Point on the Limb, 0° 55' South.** | Day of the month | Face of the arch, E. or W. | Plumb-line. | Observation of the star. | Zenith distance in revolutions and parts. | Zenith distance reduced. | Barometer. | Thermometer. | |------------------|---------------------------|-------------|--------------------------|------------------------------------------|--------------------------|------------|--------------| | Sept. 18 | E | rev. div. | rev. div. | 0° ' rev. div. | Inches. | | | | | | | | | | | | | | W | 8 19.17 | 8 53.6 | 0 55 0 34.43 | 28.8 | 64.5 | 67.5 | | | E | 9 37.05 | 9 2.2 | 35.45 | 28.8 | 66.5 | 72.0 | | | W | 8 31.87 | 9 7.5 | 34.63 | 28.8 | 65.0 | 67.0 | | | E | 10 16.65 | 9 35.3 | 40.35 | 28.8 | 65.2 | 67.2 | | | W | 8 51.59 | 9 28.2 | 35.61 | 28.8 | 66.0 | 66.0 | | | E | 8 49.25 | 8 10.5 | 38.75 | 28.8 | 65.5 | 65.5 | | | W | 8 22.08 | 8 56.0 | 33.91 | 28.8 | 59.0 | 63.0 | | | E | 9 45.92 | 9 7.0 | 38.92 | 28.8 | 66.5 | 67.0 | | | W | 9 11.63 | 9 46.4 | 34.77 | 28.8 | 59.0 | 64.0 | | | E | 8 57.40 | 8 13.4 | 44.00 | 28.8 | 52.0 | 55.5 | | | W | 8 54.83 | 9 31.1 | 35.27 | 28.8 | 60.0 | 62.0 | | | E | 9 52.90 | 9 12.0 | 40.90 | 28.8 | 64.5 | 68.0 | | | W | 9 53.38 | 9 11.3 | 42.08 | 28.8 | 62.0 | 65.0 | | | Oct. 1 | E | 9 10.95 | 36.05 | 28.8 | 64.0 | 66.5 | | | 2 | E | 9 23.18 | 10 0.3 | 28.8 | 68.5 | 65.5 | ### Observed Zenith Distances of γ Ursae. **Point on the Limb, 2° 35' North.** | Sept. 18 | E | 9 32.47 | 8 34.9 | 2 35 0 56.57 | 2 34 3.33 | 28.8 | 77.5 | 76.5 | |----------|---|---------|--------|--------------|-----------|------|------|------| | | W | 8 20.07 | 9 20.1 | 2 35 0 57.93 | 2 34 2.87 | 28.9 | 80.0 | 76.0 | | | W | 9 22.70 | 10 18.5 | 54.80 | 5.10 | 29.1 | 80.5 | 75.0 | | Oct. 3 | E | 9 10.45 | 8 2.5 | 1 7.95 | 33 52.94 | 28.7 | 72.8 | 78.5 | ### Observed Zenith Distances of η Ursae. **Point on the Limb, 1° 55' South.** | Sept. 10 | W | 8 16.58 | 8 24.4 | 1 55 0 7.82 | 1 55 7.83 | 28.1 | 63.0 | 64.5 | |----------|---|---------|--------|--------------|-----------|------|------|------| | | E | 9 26.02 | 9 13.9 | 12.12 | 12.14 | 28.8 | 84.5 | 80.5 | | | W | 8 4.60 | 8 14.1 | 9.50 | 9.51 | 28.9 | 84.0 | 82.5 | | | E | 8 50.25 | 8 34.5 | 15.75 | 15.77 | 28.9 | 79.0 | 75.0 | | | W | 9 21.40 | 9 33.5 | 12.10 | 12.12 | 29.0 | 82.8 | 80.5 | | | E | 8 54.63 | 8 30.6 | 18.03 | 18.06 | 29.1 | 80.0 | 77.0 | | | E | 10 5.25 | 9 47.7 | 16.55 | 16.57 | 29.1 | 78.5 | 72.5 | | | W | 10 6.12 | 10 15.0 | 8.88 | 8.89 | 29.1 | 84.0 | 76.0 | | | Oct. 3 | E | 9 27.63 | 9 9.2 | 18.43 | 18.46 | 29.0 | 80.0 | 76.2 | **Observed Zenith Distances of ζ Ursae.** *Point on the Limb, 3° 45' North.* | Day of the month | Face of the arch, E. or W. | Plumb-line. | Observation of the star. | Zenith distance in revolutions and parts. | Zenith distance reduced. | Barometer | Thermometer | |------------------|----------------------------|-------------|--------------------------|------------------------------------------|--------------------------|-----------|-------------| | Sept 24 | E | rev. div. | rev. div. | 3 45 0 55,60 | 3 44 4,31 | 28,9 | 72,5 | | 26 | W | 9 | 1,95 | 9 53,5 | 51,55 | 8,36 | 29,1 | | Oct. 3 | E | 9 | 50,72 | 8 50,0 | 1 0,72 | 0,18 | 29,0 | | Day of the month | Face of the arch, E. or W. | Plumb-line. | Observation of the star. | Zenith distance in revolutions and parts. | Zenith distance reduced. | Barometer | Thermometer | |------------------|----------------------------|-------------|--------------------------|------------------------------------------|--------------------------|-----------|-------------| | Sept. 18 | E | 9 | 50,42 | 8 52,5 | 5 25 0 56,92 | 5 25 57,01 | 28,8 | | Oct. 3 | W | 9 | 33,10 | 10 24,5 | 50,40 | 50,48 | 28,6 | **Observed Zenith Distances of 22 τ Herculis.** *Point on the Limb, 5° 15' South.* | Day of the month | Face of the arch, E. or W. | Plumb-line. | Observation of the star. | Zenith distance in revolutions and parts. | Zenith distance reduced. | Barometer | Thermometer | |------------------|----------------------------|-------------|--------------------------|------------------------------------------|--------------------------|-----------|-------------| | Sept. 8 | E | 7 | 35,23 | 8 0,6 | 3 5 0 23,37 | 3 4 36,59 | 28,8 | | 12 | E | 8 | 29,27 | 8 52,5 | 23,23 | 36,73 | 28,8 | | 16 | W | 9 | 17,50 | 8 47,9 | 28,00 | 31,35 | 28,9 | | 18 | W | 9 | 53,52 | 9 25,3 | 28,22 | 31,73 | 28,8 | | 19 | E | 7 | 52,87 | 8 11,0 | 23,13 | 36,83 | 28,8 | | 22 | E | 7 | 44,73 | 8 9,3 | 23,57 | 36,39 | 28,8 | | 23 | W | 8 | 58,00 | 8 27,4 | 30,60 | 29,35 | 28,7 | | 25 | E | 8 | 58,42 | 9 23,7 | 24,28 | 35,67 | 29,0 | | 26 | W | 9 | 49,10 | 9 19,8 | 29,30 | 30,65 | 29,1 | **Observed Zenith Distances of α Persei.** *Point on the Limb, 3° 5' South.* | Day of the month | Face of the arch, E. or W. | Plumb-line. | Observation of the star. | Zenith distance in revolutions and parts. | Zenith distance reduced. | Barometer | Thermometer | |------------------|----------------------------|-------------|--------------------------|------------------------------------------|--------------------------|-----------|-------------| | Sept. 8 | E | 7 | 35,23 | 8 0,6 | 3 5 0 23,37 | 3 4 36,59 | 28,8 | | 12 | E | 8 | 29,27 | 8 52,5 | 23,23 | 36,73 | 28,8 | | 16 | W | 9 | 17,50 | 8 47,9 | 28,00 | 31,35 | 28,9 | | 18 | W | 9 | 53,52 | 9 25,3 | 28,22 | 31,73 | 28,8 | | 19 | E | 7 | 52,87 | 8 11,0 | 23,13 | 36,83 | 28,8 | | 22 | E | 7 | 44,73 | 8 9,3 | 23,57 | 36,39 | 28,8 | | 23 | W | 8 | 58,00 | 8 27,4 | 30,60 | 29,35 | 28,7 | | 25 | E | 8 | 58,42 | 9 23,7 | 24,28 | 35,67 | 29,0 | | 26 | W | 9 | 49,10 | 9 19,8 | 29,30 | 30,65 | 29,1 | An Account of the Measurement Observed Zenith Distances of Capella. Point on the Limb, 7° 40' South. | Day of the month | Face of the arch, E. or W. | Plumb-line. | Observation of the star. | Zenith distance in revolutions and parts. | Zenith distance reduced. | Barometer. | Thermometer. | |------------------|---------------------------|-------------|--------------------------|------------------------------------------|--------------------------|------------|--------------| | Sept. 11 | E | rev. div. | rev. div. | ° ' rev. div. | Inches. | | | | | | 9 47:77 | 8 15:19 | 6 25 1 33:87 | 6 26 33:02 | 28:8 | 46:5 | | | | | | | | | 50:5 | | | E | 8 45:17 | 7 12:1 | 33:07 | 32:22 | 28:7 | 38:5 | | | | | | | | | 43:5 | | | W | 7 41:57 | 9 9:1 | 26:53 | 25:67 | 28:8 | 53:5 | | | | | | | | | 56:5 | | | W | 9 51:50 | 10 20:3 | 27:80 | 26:94 | 28:9 | 54:5 | | | | | | | | | 56:5 | | | E | 9 24:77 | 7 48:8 | 34:97 | 34:12 | 28:9 | 55:0 | | | | | | | | | 58:0 | | | W | 8 10:88 | 9 38:0 | 27:52 | 26:66 | 28:9 | 56:0 | | | | | | | | | 57:5 | | | E | 8 48:20 | 7 15:2 | 33:00 | 32:15 | 28:8 | 57:2 | | | | | | | | | 59:1 | | | W | 8 16:97 | 9 45:5 | 28:53 | 27:67 | 28:8 | 54:0 | | | | | | | | | 56:5 | | | E | 9 6:93 | 7 34:0 | 31:93 | 31:08 | 28:8 | 58:0 | | | | | | | | | 62:0 | | | W | 8 48:50 | 10 16:2 | 26:70 | 25:84 | 28:7 | 60:5 | | | | | | | | | 58:5 | | | E | 8 53:40 | 7 20:0 | 33:30 | 32:45 | 29:0 | 48:5 | | | | | | | | | 48:5 | | | W | 9 49:52 | 11 18:6 | 28:08 | 27:22 | 29:1 | 55:0 | | | | | | | | | 56:5 | Operations at the Royal Observatory with the Zenith Sector. April, 1802. Observed Zenith Distances of β Draconis. Point on the Limb, 0° 55' North. | April | W | 9 57:80 | 6 44:2 | ° 55 3 13:60 | ° 58 10:92 | 29:9 | 40:0 | 40:0 | |-------|------|---------|--------|--------------|------------|------|------|------| | | E | 8 35:49 | 11 40:9 | 5:41 | 2:71 | 30:1 | 38:0 | 38:0 | | | W | 10 7:84 | 6 53:0 | 13:84 | 11:16 | 29:8 | 44:0 | 44:0 | | | W | 9 24:63 | 6 11:5 | 13:13 | 10:45 | 29:5 | 42:0 | 42:0 | Observed Zenith Distances of γ Draconis. Point on the Limb, 0° 0' North. | April | W | 10 21:73 | 8 18:5 | ° 0 2 3:23 | ° 2 1:43 | 29:9 | 45:0 | |-------|------|----------|--------|------------|----------|------|------| | | W | 9 9:40 | 7 4:1 | 5:30 | 3:50 | 31:1 | 53 | | | E | 8 14:48 | 10 9:5 | 1 54:02 | 1 53:21 | 29:9 | 55 | | | E | 9 21:79 | 10 18:5| 55:71 | 54:90 | 30:1 | 38 | | | W | 9 39:52 | 7 34:4 | 2 5:12 | 2 3:32 | 29 | 44 | ### Observed Zenith Distances of 45 Draconis. **Point on the Limb, 5° 20' North.** | Day of the month | Face of the arch., E. or W. | Plumb-line. | Observation of the star. | Zenith distance in revolutions and parts. | Zenith distance reduced. | Barometer. Above. | Thermometer. Below. | |------------------|----------------------------|-------------|--------------------------|------------------------------------------|-------------------------|-------------------|-------------------| | April 19 | W | rev. div. | rev. div. | 0° 20' 45" | 0° 24' 47" | Inches. | ° | | | | | | | | | | | April 23 | E | 8 21.37 | 13 6.0 | 43.63 | 40.01 | 30.1 | 38 | | April 25 | W | 9 47.20 | 4 54.5 | 51.70 | 48.19 | 29.8 | 40 | ### Observed Zenith Distance of 46 c Draconis. **Point on the Limb, 3° 50' North.** | April 15 | W | 9 15.70 | 7 41.9 | 3 50 1 32.80 | 3 51 31.95 | 29.8 | 44 | ### Observed Zenith Distance of 51 Draconis. **Point on the Limb, 1° 36' North.** | April 19 | W | 9 48.80 | 8 55.7 | 1 35 0 52.10 | 1 35 52.19 | 31.1 | 53 | | April 23 | E | 8 43.56 | 10 27.8 | 43.34 | 43.31 | 30.1 | 38 | | April 25 | W | 8 54.53 | 7 46.0 | 49.83 | 49.91 | 29.8 | 44 | ### Observed Zenith Distance of 1 n Cygni. **Point on the Limb, 1° 30' North.** | April 23 | E | 9 20.36 | 10 42.8 | 1 30 1 22.44 | 1 31 21.53 | 30.1 | 38 | | April 25 | W | 8 29.76 | 6 58.6 | 30.16 | 29.31 | 29.5 | 51 | ### Observed Zenith Distance of 10 i Cygni. **Point on the Limb, 0° 10' South.** | April 19 | W | 11 32.42 | 11 42.6 | 0 10 0 10.18 | 0 10 10.19 | | April 23 | E | 9 36.12 | 18.42 | 18.45 | | ### Observed Zenith Distance of γ Ursae. **Point on the Limb, 3° 15' North.** | Day of the month | Face of the arch, E. or W. | Plumb-line. | Observation of the star. | Zenith distance in revolutions and parts. | Zenith distance rectified. | Barometer Above. | Thermometer Below. | |------------------|----------------------------|-------------|--------------------------|-------------------------------------------|---------------------------|-----------------|-------------------| | April 20 | E | rev. div. | rev. div. | 0° 15' 3" 58',40" | 3° 18' 55",79" | 29.9 | 50 | | 22 | E | 8 44,30 | 12 42,7 | | | | | | 23 | E | 10 36,00 | 14 36,0 | | | | | | 24 | W | 4 28,25 | 8 29,5 | | | | | ### Observed Zenith Distance of η Ursae. **Point on the Limb, 1° 10' South.** | April 16 | W | 10 13,90 | 10 40,7 | 1 10 0 26,80 | 1 10 26,84 | 29.9 | 45 | |----------|----|----------|---------|--------------|------------|------|----| | 23 | E | 3 37,50 | 3 4,6 | | | | | ### Observed Zenith Distance of 85 i Herculis. **Point on the Limb, 5° 20' South.** | April 16 | W | 11 1,59 | 11 47,9 | 5 20 0 46,31 | 5 20 46,39 | 29.0 | 40 | |----------|----|---------|---------|--------------|------------|------|----| | 19 | W | 9 40,30 | 10 30,5 | 39,26 | 39,26 | 31,5 | 53 | | 23 | E | 9 21,16 | 9 23,5 | 56,66 | 56,75 | 30,1 | 38 | Table showing the Runs of the Micrometer-screw over every 5' in the first Degree on each Side of Zero. | Right Hand Arc | Left Hand Arc | |----------------|---------------| | At | R. D. | At | R. D. | | 0° 0' | 8 55.43 | 9 16.31 | 5 4.54 | | 5° 14' | 0.88 | 4.45 | | | 5° 9' | 32.55 | 11.77 | 5 4.56 | | 10° 14' | 37.10 | 8.73 | 5 4.56 | | 10° 9' | 40.03 | 4.17 | | | 15° 14' | 44.37 | 53.67 | 5 4.50 | | 15° 9' | 19.13 | 49.17 | 5 4.50 | | 20° 14' | 23.58 | 16.13 | | | 20° 9' | 54.07 | 11.69 | 5 4.44 | | 25° 14' | 58.47 | 17.50 | 5 4.53 | | 25° 9' | 39.23 | 12.97 | | | 30° 14' | 43.64 | 4.30 | | | 30° 9' | 25.77 | 58.80 | 5 4.50 | | 35° 14' | 30.21 | 52.0 | | | 35° 9' | 58.53 | 47.53 | 5 4.47 | | 40° 15' | 4.07 | 7.83 | | | 40° 9' | 0.53 | 3.30 | 5 4.53 | | 45° 14' | 5.07 | 3.31 | | | 45° 9' | 12.47 | 57.90 | 5 4.41 | | 50° 14' | 17.02 | 12.63 | | | 50° 9' | 43.07 | 8.23 | 5 4.40 | | 55° 14' | 47.50 | 4.50 | | | 55° 9' | 41.27 | 0.03 | 5 4.47 | | 1° 13' | 45.77 | 35.0 | | | | 4.50 | 30.43 | 5 4.57 | Table for converting the Divisions shewn on the Micrometer Head into Seconds; the Space subtended by 5' on the Limb being found = 5 Revolutions 45 Divisions, as deduced from the Measurement of the Total Arches. | R. | D. | " | |----|----|-----| | 0 | 1 | 1,002 | | 0 | 2 | 2,003 | | 0 | 3 | 3,005 | | 0 | 4 | 4,007 | | 0 | 5 | 5,008 | | 0 | 6 | 6,010 | | 0 | 7 | 7,012 | | 0 | 8 | 8,013 | | 0 | 9 | 9,015 | | 0 | 10 | 10,016 | | 0 | 11 | 11,018 | | 0 | 12 | 12,020 | | 0 | 13 | 13,022 | | 0 | 14 | 14,023 | | 0 | 15 | 15,025 | | 0 | 16 | 16,027 | | 0 | 17 | 17,028 | | 0 | 18 | 18,030 | | 0 | 19 | 19,032 | | 0 | 20 | 20,033 | | 0 | 21 | 21,035 | | 0 | 22 | 22,037 | | 0 | 23 | 23,038 | | 0 | 24 | 24,040 | | 0 | 25 | 25,042 | | 0 | 26 | 26,043 | | 0 | 27 | 27,045 | | 0 | 28 | 28,047 | | 0 | 29 | 29,043 | | R. | D. | " | |----|----|-----| | 0 | 30 | 30,050 | | 0 | 31 | 31,052 | | 0 | 32 | 32,053 | | 0 | 33 | 33,055 | | 0 | 34 | 34,057 | | 0 | 35 | 35,058 | | 0 | 36 | 36,060 | | 0 | 37 | 37,062 | | 0 | 38 | 38,063 | | 0 | 39 | 39,065 | | 0 | 40 | 40,067 | | 0 | 41 | 41,068 | | 0 | 42 | 42,170 | | 0 | 43 | 43,072 | | 0 | 44 | 44,073 | | 0 | 45 | 45,075 | | 0 | 46 | 46,077 | | 0 | 47 | 47,078 | | 0 | 48 | 48,080 | | 0 | 49 | 49,082 | | 0 | 50 | 50,083 | | 0 | 51 | 51,085 | | 0 | 52 | 52,087 | | 0 | 53 | 53,088 | | 0 | 54 | 54,090 | | 0 | 55 | 55,092 | | 0 | 56 | 56,093 | | 0 | 57 | 57,095 | | 0 | 58 | 58,097 | Table for supplying the necessary Correction to the observed Zenith Distance of a Star, on account of the Expansion or Contraction of the sectorial Tube by $1^\circ$ of Heat. | Zenith distance observed | Correction for $1^\circ$ of heat | |--------------------------|---------------------------------| | | | | 1 | 0.018 | | 1 30 | 0.028 | | 2 | 0.037 | | 2 30 | 0.046 | | 3 | 0.056 | | 3 30 | 0.065 | | 4 | 0.074 | | Zenith distance observed | Correction for $1^\circ$ of heat | |--------------------------|---------------------------------| | | | | 4 30 | 0.084 | | 5 | 0.093 | | 5 30 | 0.102 | | 6 | 0.111 | | 6 30 | 0.121 | | 7 | 0.130 | | 7 30 | 0.129 | In using the above Table, the corrections are to be taken as negative, if the upper thermometer denotes the air to be hotter towards the top of the observatory than round the limb of the sector; and positive, if the reverse. Reduction of the several Observations contained in the preceding Article, from the respective Days on which they were made, to the first of January, 1802; the Equations being those for Aberration, Nutation, semi-annual solar Equation, Precession, and Refraction; with the Zenith Distances of the several Stars deduced therefrom. **Reduction of the Observations made at Dunnose.** ### β Draconis, N. | Face of limb, West. | Face of limb, East. | Zenith dist. | |---------------------|--------------------|--------------| | May 11—1° 50' 7",65 | May 13—1° 50' 0",23 | 1° 50' 3",46 | | 14 7,0 | 16 1,10 | +1,83 Mean refraction. | | June 5 6,11 | June 8 0,12 | -0,05 Temperature. | | | | +0,00 Expansion of axis. | Mean 1 50 6,88 Mean 1 50 0,04 ### γ Draconis, N. | May 11—0° 54' 0",34 | May 10—0° 53' 51",66 | Zenith dist. | |---------------------|----------------------|--------------| | 14 0,12 | 13 52,31 | 0° 53' 55",75 | | June 11 53 59,45 | 16 51,54 | +0,91 Refraction. | | | | -0,02 Temperature. | | | | -0,01 Expansion of axis. | Mean 0 53 59,39 Mean 0 53 52,11 ### 45 d Draconis, N. | June 14—6° 16' 45",24 | June 13—6° 16' 36",66 | Zenith dist. | |-----------------------|-----------------------|--------------| | 18 47,41 | 16 37,91 | 6° 16' 41",70 | | 21 45,99 | 20 37,47 | +6,29 Refraction. | | | | -0,21 Temperature. | | | | -0,12 Expansion of axis. | Mean 6 16 46,21 Mean 6 16 37,29 Mean zen. dist 6 16 47,66. Line of collimation 4,46. ### 46 c Draconis, N. | June 14—4° 43' 29",43 | June 13—4° 43' 20",76 | Zenith dist. | |-----------------------|-----------------------|--------------| | 18 26,06 | 16 19,99 | 4° 43' 24",42+4",71 (refr. &c.) = 4° 43' 28",93. | | 21 28,62 | 28 22,18 | Line of collimation 3,41. | Mean 4 43 27,86 Mean 4 43 20,93 ### 51 Draconis, N. | Face of limb, West | Face of limb, East | |-------------------|-------------------| | June 14—2° 28' 45",62 | June 13—2° 28' 38",26 | | 18 44,85 | 10 37,67 | | 21 44,85 | 20 39,01 | | Mean 2 28 45,11 | Mean 2 28 38,31 | Zenith dist. 2° 28' 41",71+2",34 (refr. &c.) = 2° 28' 44",05. Line of collimation 3,40. ### μ Draconis, N. | May 11—4° 7' 1"57 | May 13—4° 6' 51",29 | |-------------------|-------------------| | 14 57,03 | June 8 51,58 | | June 14 59,13 | 13 51,00 | | 17 58,18 | 16 51,12 | | 20 58,43 | 18 52,20 | | Mean 4 6 58,99 | Mean 4 6 51,62 | Zenith dist. 4° 6' 55",30+4", (refr. &c.) = 4° 6' 59",30. Line of collimation 3,68. ### 16 Draconis, N. | May 11—2° 42' 34",99 | June 13—2° 42' 26",55 | |-------------------|-------------------| | 14 34,17 | 16 27,73 | | 16 33,27 | 18 26,85 | | June 11 34,25 | | | 14 34,26 | | | 20 34,31 | | | Mean 2 42 34,21 | Mean 2 42 27,04 | Zenith dist. 2° 42' 30",63+2",63 (refr. &c.) = 2° 42' 33",26. Line of collimation 3,58. ### 1 κ Cygni, N. | June 14—2° 23' 26",44 | June 13—2° 23' 16",46 | |-------------------|-------------------| | 18 23,20 | 16 16,54 | | 21 20,51 | 20 17,31 | | Mean 2 23 24,38 | Mean 2 23 16,77 | Zenith dist. 2° 23' 20",58+2",28 (refr. &c.) = 2° 23' 22",86. Line of collimation 3,80. ### 10 i Cygni, N. | June 14—0° 41' 43",52 | June 13—0° 41' 35",84 | |-------------------|-------------------| | 18 43,53 | 16 36,42 | | 21 42,69 | 20 38,54 | | Mean 0 41 43,24 | Mean 0 41 36,93 | Zenith dist. 0° 41' 40",08+0",68 (refr. &c.) = 0° 41' 40",68. Line of collimation 3,15. ### γ Ursæ, N. | May 11—4° 10' 33",47 | May 9—4° 10' 28",18 | |-------------------|-------------------| | 15 30,73 | 10 28,58 | | June 5 36,05 | 13 29,82 | | 13 35,75 | 14 29,02 | | 14 34,80 | 17 30,01 | | June 8 30,24 | | | 16 30,24 | | | Mean 4 10 35,48 | Mean 4 10 29,44 | Zenith dist. 4° 10' 32",46+3",77 (refr. &c.) = 4° 10' 36",23. Line of collimation 3,02. ### η Ursae, S. | Face of limb, West | Face of limb, East | Zenith dist. | |-------------------|-------------------|--------------| | May 14—0° 18' 38",84 | May 10—0° 18' 44",08 | 0° 18' 42",61+0",32 (refr. &c.)=0° 18' 42",93. | | June 5 40,16 | June 8 47,04 | Line of collimation 3,06, | | 11 37,13 | 17 45,01 | | | 13 38,62 | 12 46,57 | | | 16 42,06 | 14 45,21 | | | 18 39,89 | 20 46,18 | | | Mean 0 18 39,48 | Mean 0 18 45,54 | | ### ζ Ursae, N. | Face of limb, West | Face of limb, East | Zenith dist. | |-------------------|-------------------|--------------| | May 11—5° 20' 34",10 | May 13—5° 20' 26",41 | 5° 20' 30",53+5",13 (refr. &c.)=5° 20' 35",66. | | June 5 34,15 | June 8 25,28 | Line of collimation 3,76. | | 11 34,42 | 14 26,96 | | | 18 34,57 | 17 26,38 | | | Mean 5 20 34,30 | Mean 5 20 26,77 | | ### 85 Herculis, S. | Face of limb, West | Face of limb, East | Zenith dist. | |-------------------|-------------------|--------------| | May 14—4° 29' 54",76 | May 10—4° 30' 0",16 | 4° 29' 57",48+4",47 (refr. &c.)=4° 30' 1",95. | | June 14 53,20 | June 13 1,39 | Line of collimation 3,46. | | Mean 4 29 53,98 | Mean 4 30 0,91 | | ### v Herculis, S. | Face of limb, West | Face of limb, East | Zenith dist. | |-------------------|-------------------|--------------| | May 14—4° 1' 25",29 | May 13—4° 1' 33",50 | 4° 1' 29",55+3",69 (refr. &c.)=4° 1' 33",24. | | June 16 26,46 | June 13 32,52 | Line of collimation 3,35. | | 5 26,51 | 16 32,56 | | | 14 26,51 | 18 32,56 | | | Mean 4 1 26,19 | Mean 4 1 32,90 | | ### 52 Herculis, S. | Face of limb, West | Face of limb, East | Zenith dist. | |-------------------|-------------------|--------------| | May 14—4° 16' 53",72 | May 13—4° 17' 0",15 | 4° 16' 57",08+4",20 (refr. &c.)=4° 17' 1",28. | | June 11 53,23 | June 8 0,60 | Line of collimation 3,76. | | 14 52,63 | 13 0,63 | | | 17 54,90 | 16 0,60 | | | 20 54,02 | 21 0,51 | | | Mean 4 16 53,70 | Mean 4 17 0,47 | | of an Arc of the Meridian. 22 τ Herculis. | Face of limb, West. | Face of limb, East. | Zenith dist. 3° 49' 33",32 + 3",78 (refr. &c.) = 3° 49' 37",10. | |---------------------|---------------------|-------------------------------------------------------------| | May 11—3° 49' 30",31 | May 10—3° 49' 38",10 | Line of collimation 3,16. | | 14 | 29,26 | | | 16 | 30,63 | | | June | June | | | 5 | 29,92 | | | 11 | 29,43 | | | 14 | 30,09 | | | 17 | 29,86 | | | 20 | 31,58 | | | Mean 3 49 30,16 | Mean 3 49 36,49 | | Capella, S. | May 12—4° 50' 55",46 | May 11—4° 50' 2",79 | Zenith dist. 4° 59' 58",81 + 4",07 (refr. &c.) = 4° 50' 2",88. | |----------------------|---------------------|-------------------------------------------------------------| | 15 | 54,02 | Line of collimation 3,31. | | June | June | | | 8 | 54,87 | | | 15 | 55,87 | | | 21 | 56,91 | | | 22 | 55,24 | | | Mean 4 50 55,49 | Mean 4 50 2,13 | | Reduction of the Observations made at Clifton, (the northern Extremity of the meridional Arc,) and the Zenith Distances of the several Stars deduced therefrom. β Draconis, S. | July 20—1° 0' 13",82—July 26—1° 0' 22",41 | Zenith dist. 1° 0' 16",89 + 0",95 (refr. &c.) = 1° 0' 17",84. | |--------------------------------------------|-------------------------------------------------------------| | 22 | 13,15 | | 28 | 12,38 Aug. | | 31 | 12,15 | | Aug. 3 | 13,39 | | 7 | 12,87 | | 3 | 13,42 | | 18 | 13,80 | | Mean 1 0 13,11 | Mean 1 0 20,68 | γ Draconis, S. | July 20—1° 56' 21",63 | 1° 56' 28",50 | Zenith dist. 1° 56' 24",86 + 1",78 (refr. &c.) = 1° 56' 26",64. | |------------------------|--------------|-------------------------------------------------------------| | 22 | 21,47 | Line of collimation 3,30. | | 26 | 21,72 | | | 29 | 21,67 | | | Aug. 1 | 22,90 | | | 11 | 20,45 | | | 13 | 21,55 | | | 18 | 21,03 | | | Mean 1 56 21,56 | Mean 1 56 28,16 | | ### An Account of the Measurement #### 45 d Draconis, N. | Face of limb, West | Face of limb, East | Zenith dist. | Line of collimation | |-------------------|-------------------|--------------|---------------------| | July 22—3° 26′ 23″,96 | July 31—3° 26′ 16″,41 | 3° 26′ 19″,63 + 3″,29 (refr. &c.) = 3° 26′ 22″,92 | 3° 72′ | #### 46 c Draconis, N. | Face of limb, West | Face of limb, East | Zenith dist. | Line of collimation | |-------------------|-------------------|--------------|---------------------| | July 20—1° 53′ 7″,60 | July 28—1° 53′ 1″,11 | 1° 53′ 4″,44 + 1″,80 (refr. &c.) = 1° 53′ 6″,24 | 3° 47′ | #### 51 Draconis, S. | Face of limb, West | Face of limb, East | Zenith dist. | Line of collimation | |-------------------|-------------------|--------------|---------------------| | Aug. 7—0° 21′ 33″,26 | July 28—0° 21′ 41″,62 | 0° 21′ 37″,78 + 0″,34 (refr. &c.) = 0° 21′ 38″,12 | 4° 15′ | #### μ Draconis, N. | Face of limb, West | Face of limb, East | Zenith dist. | Line of collimation | |-------------------|-------------------|--------------|---------------------| | July 20—1° 16′ 39″,87 | July 29—1° 16′ 34″,53 | 1° 16′ 36″,97 + 1″,23 (refr. &c.) = 1° 16′ 38″,20 | 3° 25′ | #### 16 Draconis, S. | Face of limb, West | Face of limb, East | Zenith dist. | Line of collimation | |-------------------|-------------------|--------------|---------------------| | July 30—0° 7′ 47″,75 | July 29—0° 7′ 54″,09 | 0° 7′ 51″,15 + 0″,10 (refr. &c.) = 0° 7′ 51″,25 | 3° 40′ | #### 1 κ Cygni, S. | Face of limb, West | Face of limb, East | Zenith dist. | Line of collimation | |-------------------|-------------------|--------------|---------------------| | July 20—0° 26′ 55″,72 | July 28—0° 27′ 3″,20 | 0° 26′ 59″,91 + 0″,41 (refr. &c.) = 0° 27′ 0″,32 | 3° 68′ | ### 10 Cygni, S. | Face of limb, West | Face of limb, East | |-------------------|-------------------| | July 20—2° 8' 36",86 | July 28—2° 8' 42",47 | | 29 35,01 | 31 44,05 | | 30 39,42 | Aug. 5 43,54 | | Aug. 1 37,37 | 12 45,24 | | 7 37,62 | 17 43,76 | | 9 37,56 | | | 18 35,96 | | | Mean 2 8 30,68 | Mean 2 8 43,79 | Zenith dist. 2° 8' 40",23+1",99 (refr. &c.) = 2° 8' 42",22. Line of collimation 3,55. ### γ Ursae, N. Aug. 17—1° 20' 8",84. ### ζ Ursae, N. | Face of limb, West | Face of limb, East | |-------------------|-------------------| | Aug. 5—2° 30' 10",72 | July 29—2° 30' 4",59 | | 9 12,38 | Aug. 8 4,47 | | Aug. 17 5,39 | | | Mean 2 30 11,55 | Mean 2 30 4,81 | Zenith dist. 2° 30' 8",18+2",19 (refr. &c.) = 2° 30' 10",37. Line of collimation 3,37. ### η Ursae S. | Face of limb, West | Face of limb, East | |-------------------|-------------------| | July 23—3° 8' 59",78 | Aug. 8—3° 9' 8",03 | | 26 0,93 | 17 7,85 | | Aug. 4 9 1,07 | | | Mean 3 9 0,59 | Mean 3 9 7,94 | Zenith dist. 3° 9' 4",26+2",72 (refr. &c.) = 3° 9' 6",98. Line of collimation 3,67. ### 85 Herculis, S. | Face of limb, West | Face of limb, East | |-------------------|-------------------| | July 20—7° 20' 14",13 | July 23—7° 20' 21",69 | | 28 13,19 | 5 22,57 | | 31 12,93 | 17 23,59 | | Aug. 1 12,86 | | | 7 14,71 | | | Mean 7 20 13,56 | Mean 7 20 22,61 | Zenith dist. 7° 20' 18",08+6",90 (refr. &c.) = 7° 20' 24",98. Line of collimation 4,52. ### v Herculis, S. | Face of limb, West | Face of limb, East | |-------------------|-------------------| | July 30—6° 51' 46",31 | July 21—6° 51' 52",89 | | 29 56,32 | | | Mean 6 51 54,60 | | Zenith dist. 6° 51' 50",45+6",35 (refr. &c.) = 6° 51' 56",80. Line of collimation 4,14. ### 52 Herculis, S. | Face of limb, West | Face of limb, East | |-------------------|-------------------| | July 28—7° 7' 15",02 | July 29—7° 7' 22",76 | | 30 14,21 | Aug. 8 22,63 | | Mean 7 7 14,6 | Mean 7 7 22,69 | Zenith dist. 7° 7' 18",69+6",76 (refr. &c.) = 7° 7' 25",45. Line of collimation 4,14. ### 22 τ Herculis, S. | Face of limb, West | Face of limb, East | |-------------------|-------------------| | July 30—6° 39' 51",84 | July 29—6° 40' 0",32 | | Aug. 4 50,64 | Aug. 13 39 58,02 | | 7 51,80 | | | 12 49,96 | | | Mean 6 39 51,06 | Mean 6 39 59,17 | Zenith dist. 6° 39' 55",11+6",18 (refr. &c.) = 6° 40' 1",29. Line of collimation 4,16. An Account of the Measurement α Persei, S. | Face of limb, West. | Face of limb, East. | Zenith dist. 4° 18' 31",65 + 4",37 (refr. &c.) = 4° 18" 36",02 | |-------------------|-------------------|-------------------------------------------------------------| | Aug. 8—4° 18' 29",44 | Aug. 13—4° 18' 33",15 | Line of collimation 2,28. | | 29,78 | 18 | 34,76 | | 28,87 | Mean 4 18 29,36 | Mean 4 18 33,95 | Capella, S. | Aug. 7—7° 40' 15",60 | Aug. 8—7° 40' 25",30 | Zenith dist. 7° 40' 19",06 + 6",60 (refr. &c.) = 7° 40' 25",66 | |-------------------|-------------------|-------------------------------------------------------------| | 18 | 9 | 26,46 | | 11,94 | 19 | 21,32 | | Mean 7 40 13,76 | Mean 7 40 24,36 | Reduction of the Observations made at Arbury Hill, (the intermediate Point on the meridional Arc,) and the Zenith Distances of the several Stars deduced therefrom. β Draconis, N. | Sept. 8—0° 13' 47",67 | Sept. 18—0° 13' 41",91 | Zenith dist. 0° 13' 45",61 + 0",21 (refr. &c.) = 0° 13' 45",82 | |-------------------|-------------------|-------------------------------------------------------------| | 19 | 20 | 43,61 | | 48,20 | 43,32 | | 23 | 24 | 43,90 | | 49,55 | 26 | 42,24 | | 25 | 28 | 43,54 | | 48,76 | 30 | 42,92 | | 28 | Oct. 1 | 41,94 | | 48,38 | Mean 0 13 48,33 | Mean 0 13 42,92 | γ Draconis, S. | Sept. 10—0° 42' 18",72 | Sept. 11—0° 42' 23",08 | Zenith dist. 0° 42' 22",08 + 0",65 (refr. &c.) = 0° 42' 22",73 | |-------------------|-------------------|-------------------------------------------------------------| | 19 | 18 | 25,43 | | 20 | 20 | 25,49 | | 23 | 22 | 24,84 | | 18,03 | 24 | 24,67 | | 25 | 26 | 24,08 | | 19,07 | 29 | 25,56 | | 26 | Oct. 1 | 25,50 | | 19,21 | 2 | 25,56 | | Oct. 3 | Mean 0 42 19,16 | Mean 0 42 25,01 | 45 d Draconis, S. | Sept. 8—4° 40' 25",36 | Sept. 18—4° 40' 19",99 | Zenith dist. 4° 40' 22",80 + 4",41 (refr. &c.) = 4° 40' 27",21 | |-------------------|-------------------|-------------------------------------------------------------| | 15 | 20 | 19,65 | | 29,16 | 24 | 19,22 | | 19 | 26 | 19,87 | | 28,37 | 28 | 18,86 | | 23 | 29 | 16,57 | | 25,07 | Oct. 1 | 19,89 | | 25,57 | 2 | 19,15 | | 25,03 | Mean 4 40 26,45 | Mean 4 40 19,15 | ### 46 c Draconis, N. | Face of limb, West. | Face of limb, East. | Zenith dist. 3° 7' 6",25+3",05 (refr. &c.) = 3° 7' 9",30. | |---------------------|---------------------|----------------------------------------------------------| | Sept. 15—3° 7' 9",56 | Sept. 7—3° 7' 2",31 | Line of collimation 3,21. | | 16 | 10,67 | | | 19 | 9,89 | | | 21 | 9,38 | | | 23 | 9,46 | | | 25 | 8,62 | | | 29 | 8,70 | | | 30 | 9,49 | | | Oct. 1 | 2,51 | | | 2 | 3,79 | | Mean 3° 7' 9",47 ### 51 Draconis, N. | Sept. 8—0° 52' 26",01 | Sept. 7—0° 52' 20",13 | Zenith dist. 0° 52' 23",57+0",85 (refr. &c.) = 0° 52' 24",42. | |-----------------------|-----------------------|---------------------------------------------------------------| | 16 | 27,89 | Line of collimation 2,89. | | 19 | 27,60 | | | 23 | 25,70 | | | 25 | 25,98 | | | 29 | 24,59 | | | 30 | 27,43 | | | Oct. 1 | 21,01 | | | 2 | 20,31 | | Mean 0° 52' 26",46 ### 1 ε Cygni, N. | Sept. 8—0° 47' 4",07 | Sept. 7—0° 46' 57",79 | Zenith dist. 0° 47' 2",16+0",76 (refr. &c.) = 0° 47' 2",92. | |----------------------|----------------------|-------------------------------------------------------------| | 15 | 5,02 | Line of collimation 3,22. | | 16 | 6,59 | | | 18 | 6,13 | | | 23 | 5,77 | | | 25 | 4,06 | | | 29 | 5,67 | | | 30 | 5,82 | | | Oct. 1 | 59,13 | | | 2 | 58,79 | | Mean 0° 47' 5",39 ### 10 i Cygni. | Sept. 19—0° 54' 35",59 | Sept. 18—0° 54' 40",47 | Zenith dist. 0° 54' 38",21+0",88 (refr. &c.) = 0° 54' 39",09. | |------------------------|------------------------|--------------------------------------------------------------| | 21 | 34,94 | Line of collimation 2,48. | | 23 | 36,74 | | | 25 | 36,83 | | | 27 | 35,86 | | | 29 | 35,23 | | | 30 | 34,11 | | | Mean 0° 54' 35",62 | Mean 0° 54' 40",59 | | MDCCCIII. ### γ Ursae, N. | Face of limb, West | Face of limb, East | |-------------------|-------------------| | Sept. 23—2° 34′ 12″,07 | Sept. 18—2° 34′ 5″,73 | | 26 15,28 | 5,29 | | Mean 2 34 13,67 | Mean 2 34 5,51 | Zenith dist. 2° 34′ 9″,59+2″,29 (refr. &c.) = 2° 34′ 11″, Line of collimation 4,08. ### η Ursae, S. | Sept. 10—1° 55′ 1″,14 | Sept. 20—1° 55′ 4″,41 | |-----------------------|-----------------------| | 23 54 59,80 | 24 4,84 | | 25 55 2,57 | 26 7,75 | | 30 54 57,42 | 28 5,68 | | Oct. 3 | 6,41 | | Mean 1 55 0,23 | Mean 1 55 5,82 | Zenith dist. 1° 55′ 3″,03+1″,65 (refr. &c.) = 1° 55′ 4″, Line of collimation 2,79. ### ζ Ursae, N. | Sept. 26—3° 44′ 11″,63 | Sept. 24—3° 44′ 6″,99 | |-----------------------|-----------------------| | 30 4,67 | | | Oct. 3 | 5,28 | | Mean 3 44 5,64 | Zenith dist. 3° 44′ 8″,63+3″,73 (refr. &c.) = 3° 44′ 12″, Line of collimation 3,0. ### 22 τ Herculis, S. | Sept. 3—5° 25′ 50″,78 | Sept. 18—5° 25′ 58″,80 | |-----------------------|-----------------------| | Zenith dist. 5° 25′ 54″,79+5″,03 (refr. &c.) = 5° 25′ 59″, Line of collimation 4,01. ### α Persei, S. | Sept. 16—3° 4′ 26″,57 | Sept. 8—3° 4′ 30″,66 | |-----------------------|-----------------------| | 18 27,69 | 12 31,49 | | 23 26,22 | 19 32,95 | | 26 27,10 | 22 32,91 | | 25 | 32,91 | | Mean 3 4 26,89 | Mean 3 40 32,18 | Zenith dist. 3° 4′ 29″,53+3″,07 (refr. &c.) = 3° 4′ 32″, Line of collimation 2,63. ### Capella, S. | Sept. 14—6° 26′ 12″,39 | Sept. 11—6° 26′ 19″,64 | |-----------------------|-----------------------| | 16 13,75 | 12 18,89 | | 19 13,59 | 18 21,00 | | 21 14,68 | 20 19,10 | | 23 12,93 | 22 18,03 | | 26 14,48 | 25 19,64 | | Mean 6 26 13,61 | Mean 6 26 19,39 | Zenith dist. 6° 26′ 16″,46+6″,44 (refr. &c.) = 6° 26′ 22″, Line of collimation 2,89. ### Reduction of the Observations made at the Royal Observatory, and the Zenith Distances of the several Stars deduced therefrom. #### β Draconis, N. | April 16—0° 58′ 37″,66 | April 23—0° 58′ 28″,07 | |-----------------------|-----------------------| | 25 36,02 | | | 26 34,98 | | | Mean 0 58 36,22 | Zenith dist. 0° 58′ 32″,14+0″,99 (refr. &c.) = 0° 58′ 33″, Line of collimation 4,07. of an Arc of the Meridian. γ Draconis, N. Face of limb, West. April 16—0° 2' 28",37 19 29,92 25 28,55 Mean 0° 2' 28",94 Face of limb, East. April 22—0° 2' 19",05 23 20,54 Mean 0° 2' 19",79 Zenith dist. 0° 2' 24",36+0",03 (refr. &c.) = 0° 2' 24",39. Line of collimation 4,57. 45 d Draconis, N. April 19—5° 25' 14",51 25 14,93 Mean 5° 25' 14",27 April 23—5° 25' 6",17 Zenith dist. 5° 25' 10",22+5",59 (refr. &c.) = 5° 25' 15",81. Line of collimation 4,05. 46 c Draconis, N. April 25—3° 51' 57",64. 51 Draconis, N. April 19—1° 37' 18",23 25 14,62 Mean 1° 37' 16",42 April 23—1° 37' 8",79 Zenith dist. 1° 37' 12",61+1",54 (refr. &c.) = 1° 37' 14",15. Line of collimation 3,81. 1 x Cygni. April 25—1° 31' 54",14 April 23—1° 31' 46",65 Zenith dist. 1° 31' 50",39+1",48 (refr. &c.) = 1° 31' 51",87. Line of collimation 3,74. 10 i Cygni. April 19—0° 9' 45",02 April 23—0° 9' 53",90 Zenith dist. 0° 9' 49",41+0",20 (refr. &c.) = 0° 9' 49",60. Line of collimation 4,44. γ Ursae. April 24—3° 19' 7",08 April 21—3° 18' 55",69 22 55,55 23 56,12 Mean 3° 18' 55",78 Zenith dist. 3° 19' 1",43+3",24 (refr. &c.) = 3° 19' 4",67. Line of collimation 5,65. η Ursae. April 16—1° 10' 10",19 April 23—1° 10' 17",60 Zenith dist. 1° 10' 13",85+1",22 (refr. &c.) = 1° 10' 15",07. Line of collimation 3,70. 85 i Herculis. April 16—5° 20' 20",47 April 23—5° 20' 32",04 Zenith dist. 5° 20' 25",10+5",61 (refr. &c.) = 5° 20' 30",77. Line of collimation 6,93. Capella. April 13—5° 41' 21",09 April 24—5° 41' 30",91 Zenith dist. 5° 41' 26",42+5",79 (refr. &c.) = 5° 41' 32",21. Line of collimation 4,5. 3 Q 2 Previous to my entering on the following article, it may not be improper to exhibit, under their proper points of view, the several quantities derived from observation, expressive of the differences of the zenith distances, or the deviation of the point of intersection of the meridional and horizontal wires from the true line of collimation. | At Dunnose | | |------------|---| | β Draconis | 3.42 | | γ | 3.64 | | 45 d | 4.46 | | 46 c | 3.41 | | 51 | 3.40 | | μ | 3.68 | | 16 | 3.58 | | 1 κ Cygni | 3.80 | | 10 | 3.15 | | γ Ursæ | 3.02 | | η | 3.06 | | ζ | 3.76 | | 85 Herculis| 3.46 | | v | 3.35 | | 52 | 3.76 | | 22 τ | 3.16 | | Capella | 3.31 | | At Clifton | | |------------|---| | β Draconis | 3.78 | | γ | 3.30 | | 45 d | 3.72 | | 46 c | 3.47 | | 51 | 4.15 | | μ | 3.25 | | 16 | 3.40 | | 1 κ Cygni | 3.68 | of an Arc of the Meridian. | Star | Right Ascension | |---------------|-----------------| | 10 Cygni | 3:55 | | η Ursae | 3:67 | | ζ | 3:37 | | 85 Herculis | 4:52 | | υ | 4:14 | | 52 | 4:04 | | 22 τ | 4:16 | | α Persei | 2:28 | | Capella | 5:30 | At Arbury Hill. | Star | Right Ascension | |---------------|-----------------| | β Draconis | 2:71 | | γ | 2:92 | | 45 d | 3:65 | | 46 c | 3:21 | | 51 | 2:89 | | 1 η Cygni | 3:22 | | 10 η | 2:48 | | γ Ursae | 4:08 | | η | 2:79 | | ζ | 3:00 | | 22 τ | 4:01 | | α Persei | 2:63 | | Capella | 2:89 | At Greenwich. | Star | Right Ascension | |---------------|-----------------| | β Draconis | 4:07 | | γ | 4:57 | | 45 d | 4:05 | | 51 | 3:81 | | 1 η Cygni | 3:74 | | 10 η | 4:44 | | γ Ursae | 5:65 | | η | 3:70 | | Capella | 4:50 | Amplitudes of the celestial Arc comprehended by the Stations Dunnose and Clifton. **β Draconis.** | Zenith distance at Dunnose | Ditto - Clifton | |---------------------------|----------------| | 1° 50' 52.24 | 1° 07' 8.84 | Amplitude of arc = 2° 50' 23.08 **γ Draconis.** | Zenith distance at Dunnose | Clifton | |---------------------------|---------| | 0° 53' 56.63 | | | 1° 56' 26.64 | | Amplitude of arc = 2° 50' 23.27 **45 d Draconis.** | Zenith distance at Dunnose | Clifton | |---------------------------|---------| | 6° 16' 47.66 | | | 3° 26' 22.92 | | Amplitude of arc = 2° 50' 24.74 **51 Draconis.** | Zenith distance at Dunnose | Clifton | |---------------------------|---------| | 2° 28' 44.05 | | | 0° 21' 38.12 | | Amplitude of arc = 2° 50' 22.17 **46 c Draconis.** | Zenith distance at Dunnose | Clifton | |---------------------------|---------| | 4° 43' 28.93 | | | 1° 53' 6.24 | | Amplitude of arc = 2° 50' 22.69 **16 Draconis.** | Zenith distance at Dunnose | Clifton | |---------------------------|---------| | 2° 42' 33.26 | | | 0° 7' 51.25 | | Amplitude of arc = 2° 50' 24.51 **μ Draconis.** | Zenith distance at Dunnose | Clifton | |---------------------------|---------| | 4° 6' 59.30 | | | 1° 16' 38.20 | | Amplitude of arc = 2° 50' 21.10 **10 i Cygni.** | Zenith distance at Dunnose | Clifton | |---------------------------|---------| | 0° 41' 42.68 | | | 2° 8' 42.22 | | Amplitude of arc = 2° 50' 22.90 **1 κ Cygni.** | Zenith distance at Dunnose | Clifton | |---------------------------|---------| | 2° 23' 22.86 | | | 0° 27' 0.32 | | Amplitude of arc = 2° 50' 23.18 **η Ursae.** | Zenith distance at Dunnose | Clifton | |---------------------------|---------| | 0° 18' 42.93 | | | 3° 9' 6.98 | | Amplitude of arc = 2° 50' 24.05 **γ Ursae.** | Zenith distance at Dunnose | Clifton | |---------------------------|---------| | 4° 10' 36.23 | | | 1° 20' 13.53 | | Amplitude of arc = 2° 50' 22.70 **ζ Ursae.** | Zenith distance at Dunnose | Clifton | |---------------------------|---------| | 5° 20' 35.66 | | | 2° 30' 10.37 | | Amplitude of arc = 2° 50' 25.29 **52 Herculis.** | Zenith distance at Dunnose | Clifton | |---------------------------|---------| | 4° 17' 1.28 | | | 7° 7' 25.45 | | Amplitude of arc = 2° 50' 24.17 **85 i Herculis.** | Zenith distance at Dunnose | Clifton | |---------------------------|---------| | 4° 30' 1.95 | | | 7° 20' 24.98 | | Amplitude of arc = 2° 50' 23.03 **υ Herculis.** | Zenith distance at Dunnose | Clifton | |---------------------------|---------| | 4° 1' 33.24 | | | 6° 51' 56.80 | | Amplitude of arc = 2° 50' 23.56 **22 τ Herculis.** | Zenith distance at Dunnose | Clifton | |---------------------------|---------| | 3° 49' 37.10 | | | 6° 40' 1.29 | | Amplitude of arc = 2° 50' 24.19 **Capella.** | Zenith distance at Dunnose | Clifton | |---------------------------|---------| | 4° 50' 2.88 | | | 7° 40' 25.66 | | Amplitude of arc = 2° 50' 22.78 Amplitudes of the celestial Arc comprehended by the Stations Dunnose and Arbury Hill. | Star | Zenith distance at Dunnose | Zenith distance at Arbury Hill | Amplitude of arc | |---------------|----------------------------|-------------------------------|------------------| | **β Draconis** | 1° 50' 5.24" | 0° 13' 45.82" | 1° 36' 19.42" | | **γ Draconis** | 0° 53' 56.63" | 0° 42' 22.73" | 1° 36' 19.36" | | **45 d Draconis** | 6° 16' 47.66" | 4° 40' 27.21" | 1° 36' 20.45" | | **51 Draconis** | 2° 28' 44.01" | 0° 52' 24.42" | 1° 36' 19.59" | | **46 c Draconis** | 4° 43' 28.93" | 3° 7' 9.30" | 1° 36' 19.63" | **η Ursae.** | Zenith distance at Dunnose | Zenith distance at Arbury Hill | Amplitude of arc | |----------------------------|-------------------------------|------------------| | 0° 18' 42.93" | 1° 55' 4.63" | 1° 36' 21.70" | **Capella.** | Zenith distance at Dunnose | Zenith distance at Arbury Hill | Amplitude of arc | |----------------------------|-------------------------------|------------------| | 4° 50' 2.88" | 6° 26' 22.90" | 1° 36' 20.02" | **Difference between the Parallels of Latitude of Dunnose and Greenwich.** | Star | Zenith distance at Dunnose | Zenith distance at Greenwich | Difference of latitude | |---------------|----------------------------|------------------------------|------------------------| | **β Draconis** | 1° 50' 5.24" | 0° 58' 33.13" | 0° 51' 32.11" | | **γ Draconis** | 0° 53' 56.63" | 0° 2' 24.39" | 0° 51' 32.24" | It will now be proper to exhibit the various results, as previously deduced; the amplitudes of the several arcs will then stand as follow. **Arc between Dunnose and Clifton.** | Star | Zenith Distance at Dunnose | Greenwich | Zenith Distance at Dunnose | Greenwich | Difference of Latitude | |---------------|----------------------------|-----------|----------------------------|-----------|------------------------| | β Draconis | 2° 50' 23.08 | | | | | | γ | 23.27 | | | | | | 45 d | 24.75 | | | | | | 46 c | 22.69 | | | | | | 51 | 22.17 | | | | | | 16 | 24.51 | | | | | | μ | 21.10 | | | | | | ζ Ursae | 25.29 | | | | | | γ | 22.70 | | | | | | η | 24.05 | | | | | | 1 κ Cygni | 23.18 | | | | | | 10 i | 22.90 | | | | | | 85 i Herculis | 23.03 | | | | | | v | 23.56 | | | | | | 52 | 24.17 | | | | | | 22 τ | 24.19 | | | | | | Capella | 22.78 | | | | | Mean amplitude: 2° 50' 23.38 Extreme results. Mean 23°.19, and might be rejected. Between Dunnose and Arbury Hill. | Star | Amplitude | |------------|-----------| | β Draconis | 1° 36' 19",42 | | γ | 19,36 | | 45 d | 20,45 | | 46 c | 19,63 | | 51 | 19,59 | | 1 x Cygni | 19,94 | | 10 i | 19,77 | | η Ursae | 21,70 | | Mean amplitude | 1° 36' 19",98 | Between Dunnose and Greenwich. | Star | Amplitude | |------------|-----------| | β Draconis | 0° 51' 32",11 | | γ | 32,24 | | 45 d | 31,85 | | 51 | 29,90 | | 1 x Cygni | 30,99 | | 10 i | 30,28 | | η Ursae | 31,56 | | Mean amplitude | 0° 51' 31",39 | It is very generally known that his Grace the Duke of Marlborough is possessed of an excellent quadrant, made by the late Mr. Ramsden, and that he has for some years been in the habit of using it at Blenheim. As my meridional line is not far eastward from his Grace’s observatory, the zenith distance of any star or stars there determined, from a course of accurate observations, must afford me the means of ascertaining the lengths of the degrees on the meridian, at the middle points between Blenheim and the two extremities of my arc. I therefore applied to his Grace, requesting him to favour me with any observations he might have made, and with permission to publish MDCCCIII. them, if I thought proper. His Grace was pleased to comply with my request; and I now avail myself of the advantage procured by that condescension. Blenheim Observatory. Zenith Distances of γ Draconis, reduced to the Beginning of the Year 1794, from Observations made in five successive Years, by his Grace the Duke of Marlborough. From the observations of 1794, $0^\circ 19' 17''$,32 γ Draconis south of the zenith. | Year | Zenith Distance | |------|----------------| | 1795 | 17,70 | | 1796 | 17,51 | | 1797 | 17,48 | | 1798 | 17,32 | Mean $0^\circ 19' 17'',46$. Therefore, the mean zenith distance of γ Draconis, at Blenheim, on the 1st of January, 1802, may be taken at $0^\circ 19' 23'',06$ south. The zenith distance of this star, at the same period, at the station Dunnose, as derived from the late operation, is $0^\circ 53' 56'',63$ north; therefore, $0^\circ 53' 56'',63 + 0^\circ 19' 23'',06 = 1^\circ 13' 19'',69$, is the difference of latitude between Dunnose and Blenheim observatory; and here, perhaps, it may not be improper to advert to page 675 of the Phil. Trans. for 1800, where the observed and computed latitudes are given, the former being $51^\circ 50' 24'',9$, and the latter $51^\circ 50' 28'',1$. The latitude of Dunnose is $50^\circ 37' 8'',21$, that of Greenwich being taken at $51^\circ 28' 40''$; and their difference $0^\circ 51' 31'',39$, as derived from the observations made with the new sector. Hence, $50^\circ 37' 8'',21 + 1^\circ 13' 19'',69 = 51^\circ 50' 27'',9$, must be the latitude of Blenheim, within a small part of a second of the truth. But it will be improper to dwell on this matter at present; and, therefore, I shall conclude this article with giving, in order, the subtenses in the heavens, of the different parts of my terrestrial arc. 1. Dunnose and Clifton - - $2^\circ 50' 23''$.38 2. Dunnose and Arbury Hill - - $1^\circ 36' 19.98$ 3. Arbury Hill and Clifton - - $1^\circ 14' 3.40$ 4. Dunnose and Greenwich - - $0^\circ 51' 31.39$ 5. Greenwich and Clifton - - $1^\circ 58' 51.59$ 6. Arbury Hill and Greenwich - - $0^\circ 44' 48.19$ 7. Dunnose and Blenheim - - $1^\circ 13' 19.69$ 8. Blenheim and Clifton - - $1^\circ 37' 3.69$ Determination of the Lengths of the Degrees on the Meridian, in the middle Points of the several Arcs given in the last Article. On a reference to the Phil. Trans. for 1800, it will be found, that Blenheim Observatory is 446458 feet from the perpendicular to the meridian of Dunnose. But the parallel to the perpendicular at Dunnose, from that observatory, where it cuts the meridian of the former, is about $\frac{4}{10}$ of a second in latitude north of the latter; therefore, 446498 feet may be taken for the distance of Blenheim north of Dunnose. This premised, we have the following terrestrial arcs, in conjunction with the preceding celestial ones, for computing the lengths of the several degrees. | Arcs | Feet | |-----------------------|------------| | 1. Dunnose and Clifton | 1036337 | | 2. Dunnose and Arbury Hill | 586320 | | 3. Arbury Hill and Clifton | 450017 | | 4. Dunnose and Greenwich | 313696 | | 5. Greenwich and Clifton | 722641 | | 6. Arbury Hill and Greenwich | 272624 | | 7. Dunnose and Blenheim | 446498 | | 8. Blenheim and Clifton | 589839 | $3R^2$ And, by simply dividing the terrestrial arcs by their corresponding celestial ones, and afterwards multiplying the several quotients by $3600''$, we shall get the lengths of the degrees as follows. Middle point between Dunnose and Clifton - 60820 Dunnose and Arbury Hill - 60864 Arbury Hill and Clifton - 60766 Dunnose and Greenwich - 60884 Greenwich and Clifton - 60794 Arbury Hill and Greenwich - 60849 Blenheim and Clifton - 60769 Blenheim and Dunnose - 60890 Taking the latitude of Greenwich at $51^\circ 28' 40''$, from the several arcs now given, the latitudes of their middle points are easily found; and, with the lengths of the degrees, when properly arranged, will stand as follows. | Latitude of middle point | Fathoms | |--------------------------|---------| | Arbury Hill and Clifton | 52° 50' 29'',8 60766 | | Blenheim and Clifton | 52° 38' 56',1 60769 | | Greenwich and Clifton | 52° 28' 57',7 60794 | | Dunnose and Clifton | 52° 2' 19',8 60820 | | Arbury Hill and Greenwich | 51° 51' 4',1 60849 | | Dunnose and Arbury Hill | 51° 35' 18',2 60864 | | Blenheim and Dunnose | 51° 13' 18',2 60890 | | Dunnose and Greenwich | 51° 2' 54',2 60884 | Note. The altitude of Arbury Hill, above the level of the sea, is 804 feet. The altitudes of the stations southward of Arbury Hill, are given in the former accounts of the trigonometrical operations; those to the northward of Arbury Hill may be found from the following data. At Sutton, Heathersedge, elev. 15' 25"; Gringley, dep. 18' 47".—At Castle Ring, Orpit Heights, dep. 5' 26"; Bardon Hill, dep. 6' 48"; Corley, dep. 14' 26".—At Heathersedge, Orpit Heights, dep. 20' 27".—At Clifton, Heathersedge, elev. 20' 12"; Gringley, dep. 13' 40".—At Hoilan Hill, Bardon Hill, elev. 2' 33"; Orpit Heights, elev. 12' 0"; Sutton, elev. 7' 12"—At Bardon Hill, Corley, dep. 16' 3"; Arbury Hill, dep. 16' 0"; Castle Ring, dep. 12' 30"; Sutton, dep. 19' 43"; Orpit Heights, dep. 6' 35". CONCLUSION. From this measurement it appears, that the length of a degree on the meridian, in latitude $52^\circ 2' 20''$, is 60820 fathoms. This conclusion is deduced from the supposition of the whole arc subtending an angle of $2^\circ 50' 23'',38$ in the heavens, and a distance of 1036337 feet on the surface of the earth. The length of the degree at the middle point ($51^\circ 35' 18''$) between the southern extremity of the arc and Arbury Hill, is 60864 fathoms; which is greater than the above, and exceeds it by 44 fathoms. But this degree, admitting the earth to be an ellipsoid, with the ratio of its axes as 229 to 230, should be about 10 fathoms less. If the measurement of the terrestrial arc be sufficiently correct, and the earth of an elliptical form in these latitudes, either the arcs affording the deductions are incorrect, or some material deflection of the plumb-line has taken place, at one or two stations, from the effect of attraction. Without arrogating to myself any merit from the pains taken in the performance of this undertaking, I may say, I am so perfectly convinced of the general accuracy of the whole, that I cannot for a moment doubt the collective evidence of its sufficiency. From an examination of my field books, and from the remeasurement of the chains used in our base-line on Misterton Carr, I think it is probable that an error in the whole distance, of 197 miles nearly, does not subsist to an amount of more than 100 feet, corresponding to $1''$ in the amplitude of the whole arc; and I also think it probable it cannot amount to half that quantity. The supposition of the zenith distances of the stars being generally erroneous, at any one station, cannot be admitted, unless it should be imagined, that the plane of the sector's limb was not got into that of the meridian. Such an idea, however, can scarcely be entertained, after a careful examination of the several observations, and a due attention to the means by which the instrument was made to assume its right position. Perhaps, also, I should not fail to observe, in this place, that although the instrument was always brought into the plane of each meridian by means of the telescope attached to the side of the great tube, and the azimuth circle, yet, having two good chronometers in my possession, I repeatedly verified the truth of the sector's position, by observing the transits of two stars, north and south of the zenith, at the greatest distances my arc would admit of. But, to return, if there be an error in the amplitude of the total arc, from a deflection of the plumb-line at either of the stations, it is not probable that any such deflection existed at Dunnose; as the deviation of it towards the north, from a deficiency of matter towards the channel, would tend to diminish the inequality between the lengths of the two degrees. This will be evident, on consideration. I am therefore disposed to believe that the plumb-line was drawn towards the south, from the action of matter, both at the northern extremity of the arc and at Arbury Hill, but more particularly at the first-mentioned station. If this were partly the case, and both Dunnose and Arbury Hill were free from any such prevailing cause, the total arc must be too great, if taken at $2^\circ 50' 23''$, by about $8''$, nearly answering to $2''$ on each degree. A deviation of $8''$ from the true vertical, is a large quantity; nor can the cause of it be assigned, unless it be also supposed, that the matter producing that deflection extends in a southern direction beyond Arbury Hill. If the error, though not probable, as above observed, be supposed to exist at Dunnose, it must amount to more than 10"; and that too from the effects of attraction in a southern direction, where the deficiency of matter would lead us to believe the reverse would happen. I am perfectly aware that it is possible to state a case, in which the plumb-line of a sector would deviate from the true vertical by such a quantity. Thus, for instance, in a chalky county, like the southern part of the kingdom, if the instrument were set up adjoining the terminations of two strata running east and west, one of chalk and the other of much denser materials, the effect would be as we have found it. But, at Dunnose, this argument does not apply; nor is there reason to believe, from external appearances, that it will do so, with regard either to Arbury Hill or the northern extremity of the meridional line. It was the discovery of the disagreement between the subtense in the heavens, of the whole arc, and its corresponding terrestrial one, with those of its parts, which led me to apply to his Grace the Duke of Marlborough, for the observations made at Blenheim on γ Draconis, or some other star. His Lordship's compliance with my request, is shown, from the Table of results, to be serviceable; as the arc contained between the observatory at Blenheim and Dunnose, deduced from his Grace's observations, and those made at the latter place, with the meridional distance 446498 feet, give 60890 fathoms, for the length of the degree on the meridian in latitude $51^\circ 13'$; which agrees nearly with the length of the degree at the middle point between Greenwich and Dunnose. However, under all considerations of the means by which the degree in $51^\circ 13'$ has been obtained, I am inclined to believe there is an uncertainty in it, of 6 or 7 fathoms, answering to about $\frac{1}{2}$" in latitude. But, if the measured space between his Grace's observatory and Dunnose, with its amplitude, \((1^\circ 13' 19'',69)\) be used in finding the meridional distance of the whole arc, (its corresponding amplitude,) we shall get \(2^\circ 50' 11'',80\) for its subtense; which argues a deflection from the vertical at Clifton \(= 11'',79\). If the meridional distance between Dunnose and Greenwich be used, we shall, from the same mode of proceeding, make it \(= 10'',3\). In short, the general tenor of the observations seems to prove, that the plumb-line of the sector has been drawn towards the south at all the stations; and that by attractive forces, which increase as we proceed northward. On a further prosecution of this Survey, the zenith sector will be taken forward in that direction, which will afford an opportunity of throwing further light on this interesting subject. But meridional operations carried on in insular countries, are not so likely to afford just conclusions with regard to the different lengths of the degrees, as the same operations conducted in places very remote from deep seas. From the late operations of the French Academicians it appears, that the meridional distance between Dunkirk and Barcelona is \(275792,36\) modules, the metre being \(443,296\) lines of the Peru toise \(= 0,256537\)th part of the module, at the temperature of melting ice. This meridional distance, therefore, converted into English feet, is \(3527921\). The distance between Dunkirk and Paris is \(133758\) feet, and the distance between Paris and Greenwich \(= 963954\) feet; therefore, \(830196\) feet is the distance between Greenwich and Dunkirk. The distance between Greenwich and Clifton is \(722641\) feet; hence, \(4411968\) feet is the meridional distance between Clifton and Barcelona. The latitude of Barcelona is \(41^\circ 21' 48'',8\); the latitude of Greenwich is \(51^\circ 28' 40''\); and if to this latitude we add \(1^\circ 58' 51'',59\), the arc between Clifton and Greenwich, we shall get 53° 27' 31",59 for the latitude of Clifton; and shall then have the difference of latitude between Barcelona and Clifton = 12° 5' 42",79, something more than the 30th part of the whole circumference of the earth. With this difference of latitude, and the abovementioned distance, we shall get 60795 fathoms, for the mean length of a degree on the earth's surface, in latitude 47° 24'. The latitude of Paris is 48° 50' 15"; this, with that of Clifton, gives 4° 37' 16",59 for the difference between their parallels. The meridional distance is 1686595 feet; hence, 60825 fathoms, is the length of the degree in latitude 51° 9'. With regard to the latitudes of places published in our former papers, those referred to the meridian of Greenwich are to remain uncorrected, since the computations were made with nearly the same length of a degree on the meridian, as that at the middle point, now deduced, between Dunnose and Green- wich, viz. 60884 fathoms. As to those places referred to the new meridian, viz. Dunnose, Butterton, and St. Agnes Beacon, 1" is to be added to the latitudes of them all; because the latitude of Dunnose became the standard, which was then computed to be 50° 37' 7",3, but is now found, from the zenith distances of the stars observed there and at Greenwich, to be 50° 37' 8",2. By way of Appendix to this Paper, I shall subjoin the latitudes and longitudes of those places intersected in the survey of Essex, Suffolk, &c. whose distances from their respective places of observation are given in the Phil. Trans. for 1800; this cannot but be highly useful, as they may be depended on, the interior survey of those parts having since proved that no erro- neous intersections were made. APPENDIX. Bearings of the principal Stations in the Counties of Essex, &c. from the Parallels to the Meridian of Greenwich; and likewise their Distances from that Meridian. | Names of stations. | Bearings. | Distance from meridian. | Mean. | Distance from perpendicular. | Mean. | |--------------------|-----------|-------------------------|-------|----------------------------|-------| | Severndroog | New Station, Wrotham | 46° 27' 19" SE | 71978 | 71977 E | 59145 | | Old Station, Wrotham | 38° 43' 11" NE | 71976 | 59144 S | 59144½ S | | Severndroog | Graveshend | 80° 53' 20" SE | 84888 | 84888½ E | 15434 | | New Station, Wrotham | 16° 27' 19" NE | 84889 | 15433 S | 15433½ S | | Severndroog | Langdon Hill | 68° 48' 4" NE | 96515 | 96515 E | 27920 | | Gravesend | Hadleigh | 49° 32' 3" NE | 133643 | 133643½ E | 26145 | | Langdon Hill | Halstow | 87° 15' 37" SE | 133044 | 133044 E | 26145 N | | Hadleigh | Halstow | 7° 45' 59" SW | 129041 | 129040 E | 7607 S | | Gravesend | Gads Hill | 79° 56' 53" NE | 119039 | 119039 E | 7607 S | | Gravesend | Halstow | 58° 24' 46" SE | 105603 | 105603 E | 23629 S | | Halstow | Gad's Hill | 55° 38' 32" SW | 105603 | 105603 E | 23629 S | | Gad's Hill | Sheppey | 88° 46' 1" NE | 176273 | 176273 E | 22108½ S | | Halstow | South End | 72° 55' 56" SE | 176273 | 176273 E | 22108½ S | | Hadleigh | Rayleigh | 80° 11' 2" SE | 160836 | 160836 E | 21441 N | | Sheppey | Rayleigh | 19° 31' 7" NW | 160836 | 160836 E | 21441 N | | Halsrow | Rayleigh | 11° 17' 1" SE | 138709 | 138709½ E | 40850 N | | Sheppey | Prittlewell | 30° 49' 17" NW | 138709 | 138709½ E | 40850 N | | Halstow | Canewdon | 42° 47' 6" NE | 160844 | 160844 E | 26757 N | | Sheppey | Canewdon | 17° 31' 22" NW | 160844 | 160844 E | 26757 N | | Halstow | Flagstaff | 33° 18' 22" SE | 168413 | 168413 E | 51907½ N | | Sheppey | Flagstaff | 6° 16' 7" NW | 168413 | 168413 E | 51907½ N | | Halstow | Sncerness | 86° 3' 48" SE | 170376 | 170376½ E | 10449 S | | Hadleigh | Rayleigh | 45° 6' 25" SE | 170376 | 170376½ E | 10449 S | | Rayleigh | Frierning | 9° 55' 10" NW | 130525 | 130525 E | 87654 N | | Frierning | Danbury | 71° 57' 58" NE | 130531 | 130531 E | 87664 N | | Langdon Hill | Danbury | 29° 39' 21" NE | 130531 | 130531 E | 87664 N | | Severndroog | Frierning | 42° 23' 31" NE | 83919 | 83919 E | 72488 N | | Langdon Hill | Signal Staff | 15° 46' 56" NE | 83919 | 83919 E | 72488 N | | Rayleigh | Shoeburyness | 59° 55' 0" SE | 179732 | 179732 E | 17086 N | | Langdon Hill | Old Station | 82° 35' 14" SE | 179732 | 179732 E | 17086 N | | Rayleigh | Tiptree | 13° 45' 9" NE | 156314 | 156314 E | 112785 N | | Danbury | Tiptree | 45° 44' 2" NE | 156314 | 156314 E | 112785 N | | Frierning | Tillingham | 60° 53' 59" SE | 156320 | 156320 E | 112785 N | | 'Tiptree*' | Tillingham | 54° 44' 17" SE | 200547 | 200547½ E | 81514 N | | Danbury | Steeple | 84° 58' 57" SE | 200547 | 200547½ E | 81514 N | * Triptree, by mistake, in the former part of this Survey. | Names of stations | Bearings | Distance from meridian | Mean | Distance from perpendicular | Mean | |------------------|----------|------------------------|------|----------------------------|------| | Danbury | Peldon | 62°33'13" NE | 200463 | E 123986 | N | | Tillingham | Flagstaff, St. | 83°48'39" SE | 243805 | E 119284 | N | | Peldon | Osyth Priory | 48°52'57" NE | 243812 | E 119282 | N | | Danbury | Great Tey | 30°12'45" NE | 169380 | E 154381 | N | | Peldon | Steeple | 45°38'20" NW | 169382 | E 154381 | N | | Peldon | Stoke Steeple | 0°35'41" NE | 201127 | E 187921 | N | | Great Tey | Thorp Steeple | 43°25'34" NE | 201127 | E 187921 | N | | Peldon | Thorp | 75°21'46" NE | 263163 | E 140359 | N | | Stoke | Little Bentley | 52°30'43" SE | 263164 | E 140359 | N | | Peldon | Little Bentley | 60°4'57" NE | 244846 | E 149523 | N | | Thorp | Dover Court | 63°25'21" NW | 244846 | E 149523 | N | | Little Bentley | Dover Court | 63°32'9" NE | 283323 | E 168676 | N | | Thorp | West Mersea | 35°26'59" NE | 283321 | E 168675 | N | | Tillingham | Danbury | 11°58'27" NE | 206545 | E 109809 | N | | Danbury | St. Mary's | 73°45'20" SE | 206543 | E 109811 | N | | Great Tey | Colchester | 84°22'42" SE | 202276 | E 151143 | N | | Stoke | St. Mary's Colchester | 1°47'26" SE | 202276 | E 151143 | N | | Little Bromley | Stoke | 76°2'46" NE | 234987 | E 159270 | N | | Thorp | Dover Court | 49°45'52" SE | 234988 | E 159270 | N | | Dover Court | Tattingstone | 14°37'54" NW | 250358 | E 189405 | N | | Stoke | Tattingstone | 57°50'38" NE | 250351 | E 189405 | N | | Dover Court | Rushmere | 88°17'13" NE | 250350 | E 189393 | N | | Dover Court | Falkenham | 35°36'22" NW | 270865 | E 218047 | N | | Rushmere | Woodbridge | 14°9'47" NW | 270864 | E 218047 | N | | Dover Court | Rushmere | 36°17'7" SE | 302055 | E 194188 | N | | Rushmere | Falkenham | 52°35'7" SE | 302054 | E 194189 | N | | Falckenham | Woodbridge | 69°24'43" NE | 302054 | E 194190 | N | | Woodbridge | Butley Steeple | 11°9'17" NW | 295524 | E 227311 | N | | Falckenham | Light House | 85°40'43" NE | 295524 | E 227311 | N | | Falckenham | Orford | 37°32'43" NE | 295524 | E 227311 | N | | Butley | Otley Steeple | 59°30'44" NE | 295524 | E 227311 | N | | Rushmere | Otley | 6°39'43" NE | 295524 | E 227311 | N | | Woodbridge | Henley Steeple | 47°5'17" NW | 295524 | E 227311 | N | | Otley | Copdock | 53°4'43" SW | 295524 | E 227311 | N | | Rushmere | Copdock | 33°45'47" NW | 295524 | E 227311 | N | | Henley | Copdock | 23°3'13" SW | 295524 | E 227311 | N | | Rushmere | Naughton | 60°49'13" SW | 295524 | E 227311 | N | | Copdock | Naughton | 51°26'57" NW | 295524 | E 227311 | N | | Henley | Steeple | 81°35'53" SW | 295524 | E 227311 | N | | Great Tey | Twinstead | 12°47'14" NW | 295524 | E 227311 | N | | Stoke | Steeple | 86°26'30" NW | 295524 | E 227311 | N | | Stoke | Lavenham | 28°18'20" NW | 295524 | E 227311 | N | | Glemsford | Lavenham | 87°4'35" NE | 295524 | E 227311 | N | | Stoke | Bulmer | 73°17'13" NW | 295524 | E 227311 | N | | Lavenham | Bulmer | 39°30'10" SW | 295524 | E 227311 | N | 3 S 2 | Names of stations | Bearings | Distance from meridian | Mean | Distance from perpendicular | Mean | |------------------|----------|------------------------|------|----------------------------|------| | Lavenham | Glemsford| 87° 4' 35" SW | 152635 | 152636 E | 228903 N | | Bulmer | Toppesfield* | 77° 14' 50" SW | 120796 | 120796 E | 19069 N | | Bulmer | Southweald | 39° 49' 54" NE | 61300 | 61298 E | 52599 N | | Langdon Hill | Gallywood | 54° 59' 11" NW | 61296 | 61296 E | 52596 N | | Tiptree | Common | 74° 25' 56" SW | 120796 | 120796 E | 80658 N | | Gallywood Common | Pleshey * | 17° 28' 50" NW | 93384 | 93385 E | 118787 N | | Tiptree | High Easter | 33° 14' 20" NW | 79208 | 79208 E | 120611 N | | Danbury | Hatfield Oak | 62° 7' 31" NW | 55309 | 55306 E | 127466 N | | Pleshey | Beauchamp | 77° 9' 51" NW | 55303 | 55303 E | 127464 N | | Hatfield Oak | Roding | 63° 25' 9" SW | 64941 | 64940 E | 104555 N | | Danbury | Thaxted | 31° 33' 51" NW | 77490 | 77490 E | 104556 N | | Lavenham | Spire | 60° 52' 10" SW | 77475 | 77475 E | 174002 N | | Stowe | Brentwood | 83° 34' 10" SW | 77480 | 77480 E | 173985 N | | Severndroog | Old Station, | 44° 23' 29" NE | 68984 | 68984 E | 52063 N | | Langdon Hill | High Beech | 48° 45' 17" NW | 68984 | 68984 E | 52061 N | | St. Paul's | Station, | 29° 8' 28" NE | 8117 | 8117 E | 67219 N | | Severndroog | Hampstead | 43° 14' 15" NW | 39822 | 39824 W | 32055 N | | St. Paul's | New Station, | 53° 44' 33" SW | 39826 | 39826 W | 32056 N | | Old Station, High Beech | 28° 45' 2" NE | 7661 E | 7661 E | 67264 N | | High Beech | Epping Mill | 84° 18' 44" NW | 7661 | 7661 E | 67264 N | | Severndroog | Berkhamstead Gazebo | 53° 4' 40" NE | 21742 | 21742 E | 77457 N | | High Beech | Nasing Steeple | 54° 24' 9" NE | 21742 | 21742 E | 77457 N | | Hatfield Oak | Henham on the Mount | 46° 15' 36" NW | 27987 | 27990 W | 101790 N | | Hatfield Oak | Thorley | 63° 56' 1" NW | 27993 | 27993 W | 101786 N | | Hatfield Oak | Steeple | 55° 36' 7" SW | 10875 | 10875 E | 97046 N | | Henham | Elmdon | 35° 35' 42" NE | 55710 | 55710 E | 166701 N | | Thaxted | Rickling | 71° 24' 58" SW | 55692 | 55692 E | 166701 N | | Henham | Albury | 36° 40' 8" SW | 32376 | 32376 E | 135377 N | | Elmdon | Balsham | 70° 57' 48" NW | 32356 | 32356 E | 135377 N | | Elmdon | Elmdon | 35° 5' 52" NW | 29669 | 29669 E | 203730 N | | Elmdon | Rickling | 58° 8' 32" NW | 29669 | 29669 E | 203730 N | | Henham | Albury | 22° 34' 52" SE | 40925 | 40925 E | 176657 N | | Elmdon | Balsham | 55° 59' 52" NW | 40931 | 40931 E | 176657 N | | Henham | Elmdon | 11° 37' 43" SW | 19669 | 19669 E | 155072 N | | Elmdon | Balsham | 72° 6' 30" SW | 19651 | 19651 E | 155072 N | | Thaxted | Balsham | 49° 57' 18" NE | 71969 | 71969 E | 239285 N | | Thaxted | Balsham | 4° 49' 38" NW | 71970 | 71970 E | 239278 N | * Toppesfield, by mistake, in the former part of this Survey. ### Names of stations. | Names of stations | Bearings | Distance from meridian | Mean | Distance from perpendicular | Mean | |-------------------|----------|------------------------|------|----------------------------|------| | Elmdon | Babraham | 26°18'52" NE | 48970| E | 242777| N | | Balsham | Mount | 81°22'4" NW | 48982| E | 242762| N | | Elmdon | Triplow | 13°27'58" SW | 23888| E | 227854| N | | BabrahamMount | Hornchurch| 87°1'36" NW | 51738| E | 30245| N | | Langdon Hill | Severndroog| 47°41'55" NE | 51744| E | 30248| N | | Gravesend | Purfleet Cliff| 60°30'51" NW | 53972| E | 2048| N | | Hornchurch | Severndroog| 7°57'53" NE | 17541| E | 21069| N | | Hornchurch | Barking | 74°58'39" SW | 17547| E | 21070| N | | St. Paul's | Westham | 71°14'54" NE | 2205 | E | 21387| N | | Severndroog | | 24°48'33" NW | 2264 | E | 21388| N | ### Bearings of secondary Objects, &c. | Severndroog | Chigwell | 4°30'54" NE | 18578 | E | 53508 | N | |-------------|----------|-------------|-------|---|-------|---| | Highbeech | Billericay| 54°20'37" NE| 95374 | E | 54286 | N | | Severndroog | Chapel | 32°10'59" SE| 95373 | E | 54286 | N | | Frierning | Chinney of Public House| 60°27'19" SW| 22826 | E | 13855 | N | | Barking | Rainham | 38°43'29" NW| 43722 | E | 14835 | N | | Purfleet Cliff| Steeple | 27°29'1" SW | 43725 | E | 14836 | N | | Hornchurch | Belvidere | 27°18'51" SW| 37806 | E | 3266 | N | | Purfleet | Valence Tree| 89°28'19" NW| 31338 | E | 30432 | N | | Hornchurch | Cold Harbour| 3°1'31" SW | 43138 | E | 3761 | N | | Purfleet | Chadwell | 81°1'59" NW | 43137 | E | 3760 | N | | Gravesend | Greys Steeple| 36°52'50" NW| 73799 | E | 653 | S | | Severndroog | Flagstaff, Mr. | 38°59'50" NW| 70491 | E | 2348 | N | | Chadwell | Button's | 86°49'50" NW | 70491 | E | 2347 | N | | Gravesend | West Thurrock Steeple| 52°56'50" NW| 66967 | E | 1902 | S | | Gravesend | West Tilbury| 17°38'10" NE | 89420 | E | 1181 | S | | Chadwell | Northfleet| 70°45'17" NW | 76623 | E | 12548 | S | | Gravesend | Horndon Spire| 13°10'9" NE | 92494 | E | 17072 | N | | Gravesend | Flagstaff, East| 56°2'10" NE | 98431 | E | 6312 | S | | Chadwell | Tilbury | 60°27'20" SE | 98432 | E | 6313 | S | | Gravesend | Fobbing | 34°47'40" NE | 108532| E | 18591 | N | | Halstow | Steeple | 38°2'57" NW | 108535| E | 18592 | N | | Names of stations | Bearings | Distance from meridian | Mean | Distance from perpendicular | Mean | |------------------|----------|------------------------|------|----------------------------|------| | Halstow | Thundersley Steeple | 1° 36' 20" NE | — | 130198 E | — | 33719 N | | Sheppey | Leigh Steeple | 3° 29' 48" NW | 149211 | 149211 E | 23840 | 23839 N | | Halstow | Little Wakering Steeple | 7° 58' 11" NE | 179943 | 179940 E | 31175 | 31176 N | | Prittlewell | Bank Flagstaff | 8° 38' 19" SE | 192575 | 192572 E | 30108 | 30109 N | | Canewdon | Foulness Chapel | 8° 4' 49" SE | 203200 | 203199 E | 46426 | 46426 N | | Tillingham | Grange Signal Staff | 4° 45' 13" SE | 209676 | 209676 E | 70916 | 70917 N | | Peldon | Bradwell Point | 4° 21' 35" NE | 213453 | 213453 E | 95184 | 95185 N | | Tillingham | Signal Staff | 2° 16' 41" SE | 213453 | 213453 E | 95187 | 95185 N | | Tillingham | Brightlingsea | 3° 56' 17" NE | 229383 | 229382 E | 129627 | 129627 N | | Peldon | Steeple | 7° 57' 17" SE | 229381 | 229381 E | 129628 | 129628 N | | Tillingham | Toleshunt | 4° 39' 58" NW | 173531 | 173531 E | 106122 | 106123 N | | Peldon | Major | 5° 27' 2" SW | 173531 | 173531 E | 106124 | 106124 N | | Tillingham | Tolesbury | 2° 50' 13" NW | 189052 | 189051 E | 103277 | 103278 N | | West Mersea | Steeple | 6° 31' 40" SW | 189050 | 189050 E | 103279 | 103279 N | | Tillingham | Althorn | 6° 20' 37" SW | 172511 | 172512 E | 66194 | 66192 N | | Tiptree | Steeple | 1° 10' 14" SE | 172513 | 172513 E | 66191 | 66191 N | | Althorn | Burnham | 6° 50' 23" SE | 185324 | 185324 E | 59619 | 59620 N | | Tillingham | Steeple | 3° 48' 27" SW | 185324 | 185324 E | 59621 | 59621 N | | Langdon Hill | Rettenden | 4° 18' 38" NE | 126748 | 126747 E | 57827 | 57822 N | | Rayleigh | Steeple | 3° 11' 19" NW | 126747 | 126747 E | 57817 | 57822 N | | Langdon Hill | Runwell | 4° 47' 13" NE | 121154 | 121151 E | 52743 | 52740 N | | Rayleigh | Steeple | 5° 54' 27" NW | 121148 | 121148 E | 52737 | 52740 N | | Rayleigh | Great Burghstead | 8° 34' 27" NW | 96984 | 96987 E | 46288 | 46293 N | | Danbury | Steeple * | 3° 2' 12" SW | 96990 | 96990 E | 46299 | 46299 N | | Gallywood Common | East Hanningfield Steeple | 6° 53' 54" SE | 125885 | 125884 E | 70617 | 70618 N | | Danbury | Hockley | 8° 24' 42" SW | 144794 | 144796 E | 48798 | 48798 N | | Canewdon | Steeple | 2° 9' 38" SE | 144799 | 144799 E | 48798 | 48798 N | | Danbury | Stow, St. Mary's | 6° 26' 42" NE | 147833 | 147836 E | 68360 | 63358 N | | Frierning | Stock Steeple | 7° 54' 14" SE | 99912 | 99912 E | 67262 | 67261 N | | Danbury | Southminster | 5° 19' 22" SW | 99912 | 99912 E | 67261 | 67261 N | | Tiptree | Steeple | 3° 6' 6" SE | 188765 | 188762 E | 68286 | 68289 N | | Tillingham | Layer Marney | 4° 42' 29" SW | 188760 | 188760 E | 68292 | 68292 N | | Peldon | Steeple | 2° 27' NW | 180458 | 180457 E | 126613 | 126612 N | | Peldon | St. Osyth Point | 8° 26' 29" SE | 260322 | 260323 E | 113906 | 113905 N | | Tillingham | Signal Staff | 6° 33' 1" NE | 260324 | 260324 E | 113904 | 113905 N | | Thorp Steeple | Great Clackton Sig. Staff | 26° 32' 57" SE | 272780 | 272780 E | 121112 | 121111 N | * Great Burghstead, by mistake, in the former part of this Survey. | Names of stations | Bearings | Distance from meridian | Mean | Distance from perpendicular | Mean | |------------------|----------|------------------------|------|----------------------------|------| | Dover Court | Frinton * | 10°50'11" SW | 275991 | E | 130375 | | Thorp Steeple | Steeple | 52°6'20" SE | 275992 | E | 130375 N | | Thorp | Great Clackton Steeple | 3°45'53" I SE | 261921 | E | 121481 | | Peldon | | | | | 121481 N | | Dover Court | Frinton Signal Staff | 3°49'35" SE | 285637 | E | 134068 | | Thorp | Walpot Tower | 17°48'27" SE | 285639 | E | 134068 N | | Dover Court | Cupola, Languard Fort | 8°1'29" NE | 291358 | E | 143661 | | Thorp | Ardleigh Steeple | 4°56'56" NW | 291359 | E | 143661 N | | Peldon | Frating Steeple | 2°20'12" NE | 298242 | E | 170909 | | Great Tey | Thorrington Steeple | 7°30'31" SE | 298243 | E | 170909 N | | Peldon | Kirby Steeple | 6°31'56" NE | 231313 | E | 141414 | | Thorp | Little Bentley Steeple | 8°16'44" SW | 231313 | E | 141414 N | | Dover Court | Kirby Steeple | 8°44'24" SE | 239323 | E | 138809 | | Dover Court | Braitham Steeple | 7°38'51" NW | 239324 | E | 138809 N | | Tattingstone | Harwich Steeple | 4°35'22" SW | 276355 | E | 139146 | | Dover Court | Kirby Steeple | 5°5'13" NW | 276355 | E | 139146 N | | Dover Court | Little Oakley Steeple | 4°24'59" SW | 276355 | E | 139146 | | Dover Court | Bawdsey Steeple | 5°1'49" NE | 276355 | E | 139146 N | | Dover Court | Harkstead Steeple | 4°5'45" NW | 276355 | E | 139146 | | Dover Court | Arwarton Steeple | 2°41'5" SW | 276355 | E | 139146 N | | Tattingstone | Bradfield Steeple | 7°10'38" SE | 276355 | E | 139146 | | Dover Court | Falkenham Steeple | 6°37'22" SW | 276355 | E | 139146 N | | Dover Court | Orford Steeple | 5°16'53" NE | 276355 | E | 139146 | | Dover Court | Nacton Steeple | 8°34'7" NW | 276355 | E | 139146 N | | Dover Court | Capel Steeple | 6°3'17" SE | 276355 | E | 139146 | | Stoke | Great Horksley Steeple | 8°2'14" SW | 276355 | E | 139146 N | | Great Tey | Mount Bures Steeple | 5°49'14" NE | 276355 | E | 139146 | | Great Horksley | Hollesley Steeple | 6°32'14" SW | 276355 | E | 139146 N | | Dover Court | Shottisham Steeple | 8°2'14" NE | 276355 | E | 139146 | | Dover Court | Felixstow Signal Staff | 6°45'47" SE | 276355 | E | 139146 N | * Finton, by mistake, in the former part of this Survey. | Names of stations | Bearings | Distance from meridian | Mean | Distance from perpendicular | Mean | |---------------------------|---------------|------------------------|------|----------------------------|------| | Woodbridge | Bawdsey Sig. | 318758 | | 191712 | | | Dover Court | Signal Staff | 318757 | | 191716 | | | Butley | Rendlesham | 313767 | | 239061 | | | Woodbridge | Steeple | 313755 | | 239055 | | | Dover Court | Kesgrave | 278145 | | 216905 | | | Rushmere | Steeple | 278146 | | 216903 | | | Dover Court | Waldringfield | 298893 | | 211282 | | | Rushmere | Steeple | 298900 | | 211282 | | | Dover Court | Whertstead | 258996 | | 200845 | | | Kesgrave | Steeple | 258995 | | 200843 | | | Capel Steeple | Hintlesham | 235016 | | 210623 | | | Stoke | Steeple | 235019 | | 210618 | | | Stoke | Bildestone | 202169 | | 230147 | | | Lavenham | Steeple | 202168 | | 230147 | | | Stoke | Aldham | 219654 | | 214079 | | | Bildeston | Steeple | 219654 | | 214081 | | | Naughton | Hadleigh | 214492 | | 207881 | | | Lavenham | Steeple | 214639 | | 207766 | | | Naughton | Lindsey | 199105 | | 216365 | | | Lavenham | Steeple | 199249 | | 216251 | | | Stoke | Newton | 179897 | | 204850 | | | Lavenham | Steeple | 179897 | | 204850 | | | Stoke | Grotton | 193001 | | 205823 | | | Newton | Steeple | 193001 | | 205823 | | | Bulmer | Waldingfield | 177687 | | 213569 | | | Glensford | Steeple | 177692 | | 213540 | | | Glensford | Acton Steeple | 171295 | | 218047 | | | Lavenham | Beauchamp | 140480 | | 213137 | | | Bulmer | Ch. St. Paul's| 140478 | | 213135 | | | Lavenham | Hedingham | 136127 | | 188492 | | | Toppesfield | Castle | 136129 | | 188492 | | | Lavenham | Ridgewell | 121213 | | 205317 | | | Bulmer | Steeple | 121214 | | 205316 | | | Naughton | Langham | 216543 | | 179186 | | | Stoke | Steeple | 216610 | | 179127 | | | Stoke | Earles Colne | 159472 | | 164565 | | | St. Mary's, Colch. | Steeple | 159471 | | 164565 | | | St. Mary's | West Bergholt | 189552 | | 161393 | | | Great Tey | Steeple | 189554 | | 161393 | | | Danbury | Braxted | 155021 | | 120989 | | | Great Tey | Steeple | 155022 | | 120988 | | | Braxted | Kelverdon | 157104 | | 131184 | | | Great Tey | Steeple | 157104 | | 131186 | | | Great Tey | Messing | 170301 | | 132010 | | | Kelverdon | Steeple | 170302 | | 132009 | | | Great Tey | East Thorp | 175627 | | 140237 | | | Kelverdon | | 175627 | | 140236 | | | Names of stations | Bearings | Distance from meridian | Mean | Distance from perpendicular | Mean | |------------------|----------|------------------------|------|----------------------------|------| | Tiptree | Witham Steep. | 56° 46' 32" NW | 143890 | 143888 E | 120923 | | Danbury | Tarling | 75° 58' 23" NW | 129390 | 129388 E | 119511 | | Danbury | Steeple | 2° 3° 23" NW | 129386 | 129388 E | 119516 | | Pleshey | Felstead | 13° 41' 16" NE | 98214 | 98210 E | 138616 | | Danbury | Steeple | 32° 23' 31" NW | 98207 | 98210 E | 138613 | | Pleshey | Great Leigh | 81° 44' 16" NE | 118041 | 118041 E | 122359 | | Felstead | Steeple | 50° 39' 44" SE | 118041 | 118041 E | 122363 | | Pleshey | Great Baddow | 33° 23' 53" SE | 114190 | 114191 E | 87226 | | Danbury | Steeple | 88° 27' 53" SW | 114191 | 114191 E | 87226 | | Pleshey | Chelmsford | 29° 41' 53" SE | 107349 | 107349 E | 94258 | | Danbury | Steeple | 74° 2° 1" NW | 107350 | 107349 E | 94288 | | Danbury | Whittle | 82° 41' 29" NW | 97251 | 97250 E | 91931 | | Pleshey | Steeple | 8° 41' 33" SE | 97249 | 97249 E | 91942 | | Gallywood | Roxwell | 43° 43' 26" NW | 86085 | 86986 E | 99902 | | Pleshey | Steeple | 18° 43' 10" SW | 86987 | 86986 E | 99903 | | Gallywood | White Roding | 51° 38' 40" NW | 59967 | 59967 E | 116602 | | Pleshey | Steeple | 86° 15' 55" SW | 59967 | 59967 E | 116604 | | Frierning | Doddington | 78° 55' 28" SW | 67638 | 67644 E | 69301 | | Southweald | Steeple | 20° 48' 47" NE | 67651 | 67644 E | 69308 | | Southweald | Theydon | 54° 3° 14" NW | 36122 | 36125 E | 70851 | | Epping Mill | Mount Steep. | 65° 23' 14" SE | 36128 | 36125 E | 70867 | | Southweald | Navestock new | 4° 50' 14" NW | 60484 | 60485 E | 62217 | | Theydon Mount | Mill | 70° 29' 14" SE | 60487 | 60485 E | 62226 | | Southweald | Theydon Garnon Steeple | 59° 21' 14" NW | 29374 | 29363 E | 71511 | | Theydon Mount | Havering | 85° 20' 14" NW | 29351 | 29363 E | 71461 | | Theydon Mount | Steeple | 16° 39' 44" SE | 42172 | 42177 E | 50654 | | Theydon Garnon | | 31° 42' 14" SE | 42183 | 42177 E | 50654 | | Severndroog | Cupola at Woodford | 10° 24' 56" NW | 4584 | 4584 E | 47329 | | Highbeech | | 10° 4° 28" SW | 4584 | 4584 E | 47331 | | Southweald | Ruins near | 69° 1° 52" SW | 13358 | 13357 E | 34223 | | Highbeech | Ilford | 9° 1° 28" SE | 13356 | 13357 E | 34227 | | Nasing | Hunsdon | 5° 57° 9 NE | 12836 | 12839 E | 115758 | | Berkhamptstead | Steeple | 71° 6° 45" NE | 12843 | 12839 E | 115758 | | Huntsdon | Broxbourn | 40° 38° 9 SW | 3021 | 3020 W | 97376 | | Nasing | Steeple | 88° 37° 51" NW | 3020 | 3020 W | 97378 | | Danbury | Willingale | 81° 23° 51" NW | 70724 | 70725 E | 96710 | | Hatfield Oak | Spain Steeple | 26° 38° 16" SE | 70726 | 70725 E | 96716 | | Danbury | Braintree | 5° 52° 1 NW | 124508 | 124510 E | 146272 | | Felstead | Steeple | 73° 47° 14" NE | 124513 | 124510 E | 146266 | | Hatfield Oak | Harlow Steep. | 52° 44° 34" SW | 33842 | 33846 E | 111140 | | Berkhamptstead | Gazebo | 81° 29° 13" NE | 33850 | 33846 E | 111023 | | Hatfield Oak | Sabridgeworth | 74° 50° 17" SW | 34982 | 34959 E | 121958 | | Nasing | Steeple | 43° 48° 2 NE | 34936 | 34959 E | 122044 | MDCCCLIII. | Names of stations | Bearings | Distance from meridian | Mean | Distance from perpendicular | Mean | |-------------------|----------|------------------------|------|----------------------------|------| | Albury | Bishop Stortford Steeple | 54° 29' 24" SE | 35934 | 143459 E | 143454 N | | Henham | Farnham | 79° 27' 59" NW | 34427 | 154725 E | 154723 N | | Stanstead Mountfitchet Steeple | 69° 37' 6" SW | 34423 | 154721 E | 154721 N | | Albury | Stanstead Mountfitchet | 84° 18' 27" SE | 47531 | 152294 E | 152289 N | | Henham | Meesdon Mill | 69° 20' 30" NW | 19158 | 180479 E | 180483 N | | Albury | Newport | 41° 50' 8" NE | 48409 | 185013 E | 185010 N | | Rickling | Steeple | 45° 1' 52" SE | 48407 | 185007 E | 185007 N | | Balsham | Shudy Camps* | 25° 17' 50" SE | 82115 | 217814 E | 217818 N | | Elmdon | Ashdon | 55° 23' 10" SW | 68848 | 208661 E | 208660 N | | Balsham | Steeple | 5° 49' 20" SW | 68848 | 208659 E | 208659 N | **Bearings of the principal Stations of the western Parts of Kent, &c. &c.** | Frant | Sevenoaks | 19° 20' 53" NW | 42962 | 83270 E | 83270 S | | Botley Hill | Mill | 76° 21' 7" SE | 42961 | 83271 E | 83271 S | | Frant | Chiddingstone | 41° 38' 3" NW | 33852 | 106413 E | 106403 S | | Sevenoaks Mill | Steeple | 21° 31' 57" SW | 33848 | 106394 E | 106394 S | | Frant | Mount Sion | 6° 35' 46" NW | 55693 | 80967 E | 80962 S | | Chiddingstone | East Peckham | 40° 38' 14" NE | 55690 | 80957 E | 80957 S | | Frant | Steeple | 82° 45' 16" SE | 87145 | 84960 E | 84960 S | | Mount Sion | Tudeley | 32° 3' 44" SW | 73465 | 106804 E | 106804 S | | East Peckham | Steeple | 34° 31' 16" SE | 73465 | 106803 E | 106803 S | | Sevenoaks | Seal Chart | 65° 21' 5" NE | 59673 | 75601 E | 75601 S | | Botley Hill | Tunbridge | 87° 22' 55" SE | 63789 | 102135 E | 102135 S | | Sevenoaks | Steeple | 8° 48' 55" SE | 63789 | 102135 E | 102135 S | | Seal Chart | Orford Mount | 36° 37' 55" NW | 47503 | 59233 E | 59233 S | | Sevenoaks | Norwood Station, Well | 10° 42' 5" NE | 47503 | 59234 E | 59234 S | | Severndroog | Hill | 25° 45' 47" NE | 34093 | 45636 E | 45636 S | | Weli Hill | Crayford | 9° 14' 45" NE | 40173 | 45638 E | 45638 S | | Severndroog | Steeple | 80° 50' 1" SE | 40173 | 45638 E | 45638 S | | Crayford | Ash Steeple | 38° 53' 55" SE | 68780 | 43740 E | 43740 S | | Well Hill | Northfleet | 86° 52' 25" NE | 68780 | 43742 E | 43742 S | | Gad's Hill | Steeple | 69° 4' 54" NW | 76615 | 12548 E | 12548 S | | Haltstow | Steeple | 84° 36' 53" SW | 76614 | 12549 E | 12549 S | | Sheppey | Hern Hill | 48° 45' 30" SE | 220216 | 60633 E | 60633 S | | Frinstead | Stockbury | 80° 51' 12" NE | 220217 | 60633 E | 60633 S | | Hern Hill | Steeple | 85° 47' 30" NW | 148806 | 55379 E | 55379 S | | Sheppey | Frinstead | 39° 32' 30" SW | 148806 | 55379 E | 55379 S | | Sheppey | Frinstead | 15° 23' 54" SW | 163132 | 698248 E | 698248 S | * Shady Camps, by mistake, in the former part of this Survey. ### Bearings of the secondary and inferior Objects, &c. of the western Parts of Kent. | Names of stations | Bearings | Distance from meridian | Mean | Distance from perpendicular | Mean | |-------------------|----------|------------------------|------|----------------------------|------| | Frant | Bidborough | 16° 51' 0 NW | 54785 | 54786 E | 113503 | | Botley | Steeple | 53° 21' 9 SE | 54787 | | 113496 | | Frant | Station near Bidborough Church | 20° 46' 3 NW | 52687 | 52685 E | 113000 | | Chiddingstone | Tree near Kibben's Cross | 57° 9' 11 SE | 83513 | 83515 E | 126687 | | Frant | Cowden | 60° 56' 36 NE | 83518 | | 126691 | | Station near Bidborough Church | 67° 18' 3 NW | 23647 | 23679 E | 122273 | | Station near Bidborough | 72° 17' 27 SW | 23712 | | 122268 | | Leigh Steeple | 15° 18' 3 NW | 49720 | 49731 E | 102152 | | Mount Sion | 15° 39' 57 SW | 49742 | | 102175 | | Frant | Station, Ide Hill | 31° 32' 33 NW | 29621 | 29616 E | 85152 | | Chiddingstone | Eatonbridge* | 38° 26' 27 SW | 15562 | 15569 E | 102848 | | Mount Sion | Hadlow | 62° 9' 16 SE | 78053 | 78055 E | 92775 | | Peckham | Steeple | 49° 18' 44 SW | 78058 | | 92779 | | Otford Mount | Sundrich | 49° 33' 5 SW | 29901 | 29901 E | 74241 | | Seal Chart | Ketson Common Windmill| 86° 10' 47 NW | 7615 | 7614 E | 43868 | | Well Hill | Hayes Common Flagstaff| 82° 24' 47 NW | 6068 | 6068 E | 41903 | | Norwood | Addington | 84° 34' 43 SW | 11919 | 11912 E | 43611 | | Hayes Common | Norwood | 21° 16' 47 SE | 1196 | | 43606 | | Well Hill | Severndroog | Station, Farnborough | 84° 46' 47 NW | 22492 | 22491 E | 44576 | | Farnborough | St. Mary's | 11° 47' 47 SE | 22491 | | 44577 | | Well Hill | Cray | 15° 41' 13 NE | 26553 | 26553 E | 30116 | | Well Hill | Halstead | 31° 47' 27 SW | 29536 | 29535 E | 52990 | | Norwood | Bromley | 59° 50' 3 SE | 29535 | | 52990 | | Norwood | Bromley | 85° 1' 7 SE | 3304 | 3303 E | 26574 | | Severndroog | Bromley | 25° 29' 23 SW | 3303 | | 26572 | | Bromley | Hayes Steeple | 6° 39' 47 SE | 4441 | | 36311 | | Well Hill | Lewisham | 72° 33' 47 NW | 4453 | 4447 E | 36326 | | Severndroog | Chislehurst | 19° 48' 37 NW | 3352 | 3353 W | 8096 | | Severndroog | New Cross | 51° 47' 59 NW | 9490 | 9490 W | 8096 | * Edenbridge, by mistake, in the former part of this Survey. | Names of stations | Bearings | Distance from meridian | Mean | Distance from perpendicular | Mean | |------------------|----------|------------------------|------|----------------------------|------| | Severndroog | Eastcombe| 50° 43' 59" NW | 86 | 86 E | 7332 | | New Cross | Point | 41° 21' 1" NE | 87 | | 7332 | | Severndroog | Woolwich | 1° 4° 59" NW | 13855| 13853 E | 5556 | | Eastcombe Point | Steeple | 82° 38' 59" SE | 13852| | 5557 | | Crayford | Bexley Steeple | 41° 21' 39" SW | 35426| 35425 E | 13679| | Severndroog | Well Hill | 52° 33' 15" NW | 15965| 15965 E | 31752| | Crayford | Charlton Farm | 45° 53' 45" SW | 15965| | 31751| | Crayford | Dartford Brent | 69° 26' 13" SE | 54059| 54060 E | 13496| | Ash | Mill | 25° 57' 6" NW | 54061| | 13497| | Ash | Hartley Steeple | 29° 56' 5" NE | 72706| 72711 E | 36922| | Northfleet | Ridley Steeple | 64° 4' 45" SE | 73446| 73446 E | 46009| | Northfleet | Gads Hill | 5° 32' 35" SW | 73446| | 46009| | Gravesend | Cliff Steeple | 24° 3' 15" NE | 113741| 113741 E | 5396 | | Halstow | Gravesend | 70° 49' 7" NE | 113742| | 5397 | | Gravesend | Steeple | 84° 19' 23" SW | 84513| 84517 E | 12033| | Halstow | Chalk Steeple | 71° 45' 9" SW | 96111| 96110 E | 12082| | Gravesend | Guard Room | 74° 54' 24" SE | 96109| | 18464| | Gads Hill | Lower Hope | 3° 41' 11" NE | 107247| 107247 E | 1895 | | Gravesend | Point | 52° 13' 26" NE | 107247| | 1894 | | Gads Hill | Flagstaff, Tilbury Fort | 52° 58' 28" NW | 86260| 86260 E | 9039 | | Gravesend | Sheppey | Rainham | 86260| | 9041 | | Gads Hill | Steeple | 62° 21' 33" SE | 139483| 139484 E | 41373| | Halstow | Swanscombe | 84° 51' 25" SW | 70403| 70463 E | 41372| | Gads Hill | Spire | 72° 59' 24" NW | 70464| | 12880| | Halstow | Southfleet | 75° 19' 30" SW | 73187| 73187 E | 12879| | Gravesend | Steeple | 59° 50' 13" SW | 73187| | 12879| | Gravesend | Shorn Mill | 61° 26' 17" SE | 98017| 98025 E | 22234| | Halstow | Sheppey | Gillingham | 98034| | 22234| | Halstow | Steeple | 78° 54' 49" SW | 128724| 128724 E | 22580| | Gillingham | St. James's, Isle of Grain | 54° 20' 32" NE | 163871| 163871 E | 22586| | Sheppey | Friendsbury | 37° 57' 19" NW | 163871| | 31425| | Gads Hill | Steeple | 87° 3' 26" NW | 115632| 115631 E | 31427| | Sheppey | Star Inn | 65° 10' 37" NE | 115631| | 6210 | | Halstow | Sheppey | 71° 18' 17" SW | 128656| 128656 E | 6209 | | Sheppey | Upper Bell Inn | 62° 18' 51" SW | 116532| 116532 E | 18991| | Halstow | Upchurch | 15° 16' 0" SW | 116533| | 18991| | Gads Hill | Steeple | 63° 9' 35" SW | 148260| 148250 E | 53454| | Frinstead | Hucking Spire | 77° 54' 35" NW | 148260| | 53441| | Sheppey | | | 147822| 147822 E | 36283| | | | | 147822| | 36266| | | | | 147822| | 66545| | | | | 147822| | 66545| ### Names of stations | Bearings | Distance from meridian | Mean | Distance from perpendicular | Mean | |----------|------------------------|------|----------------------------|------| | Hern Hill | East Church | 34° 30' 32" NW | 196669 | 196678 E | 26383 | 26376 S | | Sheppey | Milton Steeple | 57° 27' 7" SW | 169440 | 169445 E | 43761 | 43758 S | | Milon | Iwade Steeple | 14° 54' 14" NW | 165705 | 165702 E | 29667 | 29685 S | | Sheppey | Witchling | 73° 23' 12" SW | 170790 | 170789 E | 75380 | 75380 S | | Frinstead| Steeple | 54° 2' 13" SE | 170789 | 170789 E | 75380 | 75380 S | | Hern Hill| Sheldwich | 56° 6' 30" SW | 202302 | 202291 E | 72667 | 72675 S | | Sheppey | Steeple | 27° 12' 48" SE | 202280 | 202280 E | 72682 | 72675 S | | Sheldwich| Queenborough | 31° 53' 48" NW | 170208 | 170213 E | 21124 | 21128 S | | Sheppey | Steeple | 80° 52' 4" NW | 170219 | 170219 E | 21133 | 21128 S | | Halstow | St. Mary's | 77° 55' 24" NE | 135978 | 135977 E | 6123 | 6123 S | | Hadleigh | Steeple | 4° 8' 17" SE | 135977 | 135977 E | 6123 | 6123 S | | Hern Hill| Peversham | 77° 56' 30" NW | 204931 | 204930 E | 57368 | 57368 S | | Sheppey | Steeple | 39° 6' 8" SE | 204930 | 204930 E | 57368 | 57368 S | ### Latitudes and Longitudes of the preceding Stations and Objects, referred to the Meridian of Greenwich. | Names of stations | Latitudes | Longitudes | |-------------------|-----------|------------| | Highbeech Station, Hampstead | 51° 39' 42.5" | 0° 2' 8.3" E | | New Station, Wrotham | 51° 33' 55.4" | 0° 10' 28.0" W | | Station, Gravesend | 51° 26' 5.9" | 0° 22' 15.6" E | | Langdon Hill | 51° 33' 12.5" | 0° 25' 22.1" E | | Hadleigh | 51° 32' 52.5" | 0° 35' 7.4" E | | Halstow | 51° 27' 20.3" | 0° 33' 50.7" E | | Gads Hill | 51° 24' 43.8" | 0° 27' 40.2" E | | Sheppey | 51° 24' 23.2" | 0° 46' 11.5" E | | Rayleigh | 51° 35' 17.0" | 0° 36' 29.2" E | | Prittlewell | 51° 32' 56.2" | 0° 42' 16.2" E | | Canewdon | 51° 37' 3.4" | 0° 46' 15.5" E | | Staff, Sheerness | 51° 11' 21.6" | 0° 44' 25.7" E | | Danbury | 51° 42' 59.3" | 0° 34' 26.0" E | | Fierning | 51° 40' 32.5" | 0° 22' 7.0" E | | Purfleet Cliff | 51° 28' 59.4" | 0° 14' 9.9" E | | South End | 51° 32' 4.4" | 0° 42' 15.5" E | | Staff, Shoeburyness | 51° 31' 19.1" | 0° 47' 12.6" E | | Tiptree | 51° 47' 2.2" | 0° 41' 17.8" E | | Tillingham | 51° 41' 52.7" | 0° 52' 52.9" E | | Peldon | 51° 58' 50.3" | 0° 53' 11.4" E | | Flagstaff, St. Osyth Priory | 51° 47' 57.9" | 1° 4' 25.7" E | | Great Tey | 51° 53' 53.2" | 0° 44' 49.9" E | | Stoke | 51° 59' 20.4" | 0° 53' 22.6" E | | Thorp | 51° 51' 23.2" | 1° 9' 38.3" E | | Little Bentley | 51° 52' 56.3" | 1° 4' 49.7" E | | Dover Court | 51° 55' 59.1" | 1° 15' 6.1" E | | St. Mary's, Chester | 51° 53' 17.7" | 0° 53' 33.7" E | | West Mersea | 51° 46' 29.8" | 0° 54' 33.3" E | | Little Bromley | 51° 54' 43.4" | 0° 39' 16.8" E | | Tattingstone | 51° 59' 39.4" | 0° 41' 55.5" E | | Rushmere | 52° 4' 7.3" | 1° 12' 0.8" E | | Falkenham | 51° 56' 2.2" | 1° 20' 4.0" E | | Woodbridge | 52° 5' 34.6" | 1° 18' 36.8" E | | Butley | 52° 5' 53.7" | 1° 27' 39.8" E | | Orford Light House | 52° 5' 0.1" | 1° 34' 13.6" E | | Otley | 52° 8' 54.1" | 1° 13' 2.5" E | | Names of stations | Latitudes | Longitudes | |---------------------------|-----------|------------| | Henley | 52° 7' 29" | 1° 8' 57.2"E | | Copdock | 52° 1' 51.9" | 1° 5' 13.2"E | | Naughton | 52° 6' 3.5" | 0° 56' 56.7"E | | Twinstead | 51° 59' 48.4" | 0° 42' 47.2"E | | Lavenham | 52° 6' 19.1" | 0° 47' 27.0"E | | Bulmer | 52° 1' 41.5" | 0° 41' 8.6"E | | Glemsford | 52° 6' 8.8" | 0° 40' 36.4"E | | Toppesfield | 52° 0' 28.1" | 0° 32' 4.1"E | | Gallywood Common | 51° 41' 51.8" | 0° 27' 47.7"E | | Pleshey | 51° 48' 8.0" | 0° 24' 40.8"E | | High Easter | 51° 48' 26.9" | 0° 20' 56.1"E | | Hatfield Oak | 51° 49' 35.5" | 0° 14' 37.4"E | | Beauchamp Roding | 51° 45' 48.9" | 0° 17' 8.8"E | | Thaxted | 51° 57' 13.1" | 0° 20' 32.7"E | | Southweald | 51° 37' 17.4" | 0° 16' 8.1"E | | Brentwood | 51° 37' 11.8" | 0° 18' 9.5"E | | New Station | | | | Highbeech | 51° 39' 42.9" | 0° 2' 1.1"E | | Epping Mill | 51° 41' 23.3" | 0° 5' 43.8"E | | Berkhamstead Gazebo | 51° 45' 23.0" | 0° 7' 23.3"E | | Henham on the Mount | 51° 56' 1.7" | 0° 14' 45.7"E | | Thorley | 51° 50' 53.8" | 0° 8' 33.2"E | | Elmdon | 52° 2' 7.3" | 0° 8' 3.8"E | | Rickling | 51° 57' 40.3" | 0° 10' 51.2"E | | Albury | 51° 54' 8.1" | 0° 5' 12.4"E | | Balsham | 52° 7' 56.1" | 0° 19' 9.6"E | | Babraham Mount | 51° 32' 38.5" | 0° 12' 52.1"E | | Triplow | 52° 6' 5.0" | 0° 6' 21.3"E | | Hornchurch | 51° 33' 37.3" | 0° 13' 36.1"E | | Barking | 51° 32' 7.5" | 0° 4' 36.5"E | | Westham | 51° 32' 10.6" | 0° 0' 35.7"E | | Chigwell | 51° 37' 27.2" | 0° 4' 53.4"E | | Billericay | 51° 37' 32.5" | 0° 25' 6.5"E | | Public House | 51° 30' 56.3" | 0° 5' 59.6"E | | Rainham | 51° 31' 5.7" | 0° 11' 29.0"E | | Belvidere | 51° 29' 11.7" | 0° 9' 55.3"E | | Valence Tree | 51° 33' 39.6" | 0° 8' 14.2"E | | Cold Harbour | 51° 29' 16.5" | 0° 11' 19.3"E | | Chadwell | 51° 28' 53.4" | 0° 22' 10.9"E | | West Tilbury | 51° 28' 26.1" | 0° 23' 27.7"E | | Greys Steeple | 51° 29' 1.7" | 0° 18' 30"E | | West Thurrock | 51° 28' 20.0" | 0° 17' 34.2"E | | Northfleet | 51° 26' 34.6" | 0° 20' 5.4"E | | Horndon | 51° 31' 25.7" | 0° 24' 17.8"E | | Flagstaff, East Tilbury | 51° 27' 36.0" | 0° 25' 49.2"E | | Fobbing Steeple | 51° 31' 39.8" | 0° 28' 30.7"E | | Thundersley | 51° 34' 7.4" | 0° 34' 13.9"E | | Leigh | 51° 32' 28.7" | 0° 39' 12.6"E | | Little Wakering | 51° 33' 38.0" | 0° 47' 18.3"E | | Bank Flagstaff | 51° 33' 26.0" | 0° 50' 37.5"E | | Foulness Chapel | 51° 36' 5.7" | 0° 53' 28.1"E | | Tillingham Grange Signal Staff | 51° 40' 6.2" | 0° 55' 15.2"E | | Flagstaff, Bradwell Point | 51° 44' 5.0" | 0° 56' 19.8"E | | Brightlingsea | 51° 49' 42.3" | 1° 0' 39.5"E | | Tolleshunt Major | 51° 45' 57.2" | 0° 45' 49.5"E | | Tolesbury | 51° 45' 27.6" | 0° 49' 54.9"E | | Althorn | 51° 39' 23.8" | 0° 45' 26.8"E | | Burnham | 51° 38' 17.7" | 0° 48' 48.2"E | | Rettenden | 51° 38' 5.2" | 0° 33' 22.4"E | | Runwell | 51° 37' 15.6" | 0° 31' 53.4"E | | Great Burstead | 51° 36' 13.6" | 0° 25' 31.2"E | | East Hanningfield | 51° 40' 11.4" | 0° 33' 10.2"E | | Hockley | 51° 36' 34.9" | 0° 38' 6.3"E | | Stow, St. Mary's | 51° 39' 47.4" | 0° 38' 57.1"E | | Stock Steeple | 51° 39' 40.0" | 0° 26' 19.3"E | | Southminster | 51° 39' 42.7" | 0° 49' 44.0"E | | Layer Marney | 51° 49' 13.7" | 0° 47' 42.6"E | | St. Osyth Point Signal Staff | 51° 47' 3.0" | 1° 8' 46.5"E | | Great Clacton Signal Staff | 51° 48' 12.1" | 1° 12' 5.9"E | | Friotou Steeple | 51° 30' 26.8" | 1° 12' 28.4"E | | Flagstaff, Frinton | 51° 50' 17.8" | 1° 15' 33.4"E | | Walton Tower | 51° 51' 51.2" | 1° 17' 6.8"E | | Cupola, Languard Fort | 51° 56' 18.5" | 1° 19' 3.9"E | | Arcleigh | 51° 55' 34.3" | 1° 59' 1.5"E | | Frating | 51° 51' 38.2" | 1° 1' 12.8"E | | Thorntonington | 51° 51' 10.0" | 1° 3' 19.4"E | | Kirby | 51° 51' 9.3" | 1° 13' 7.4"E | | Brantham | 51° 57' 56.4" | 1° 4' 15.5"E | | Harwich | 51° 56' 43.3" | 1° 17' 7.8"E | | Little Oakley | 51° 54' 37.3" | 1° 12' 42.9"E | | Bawdsey | 52° 0' 38.8" | 2° 24' 52.1"E | | Harkstead | 51° 58' 20.2" | 1° 1' 25.2"E | | Arwarton | 51° 57' 56.8" | 1° 13' 42.9"E | | Bradfield | 51° 56' 2.2" | 1° 6' 56.5"E | | Orford | 52° 5' 40.9" | 1° 31' 54.2"E | | Names of stations | Latitudes | Longitudes | |------------------|-----------|------------| | Nacton | 52° 0' 34.5" | 1° 13' 34.6" E | | Capel | 52° 0' 10.6" | 1° 2' 6.9" E | | Great Horksley | 51° 57' 16.5" | 0° 51' 58.4" E | | Mount Bures | 51° 57' 27.8" | 0° 46' 11.7" E | | Hollesley | 52° 2' 48.7" | 1° 25' 38.4" E | | Shottisham | 52° 3' 5.2" | 1° 22' 50.8" E | | Felixstow Staff | 51° 57' 56.9" | 1° 22' 5.1" E | | Bawdsey Signal | | | | Staff | 51° 59' 39.8" | 1° 24' 36.6" E | | Rendlesham | 52° 7' 27.2" | 1° 23' 31.5" E | | Kesgrave | 52° 7' 14.9" | 1° 14' 2.2" E | | Waldringfield | 51° 56' 56.1" | 1° 19' 26.0" E | | Whertstead | 52° 1' 19.6" | 1° 8' 47.1" E | | Hintlesham | 52° 2' 59.4" | 1° 2' 27.3" E | | Bildestone | 52° 1' 50.5" | 0° 53' 40.0" E | | Aldham | 52° 3' 35.5" | 0° 58' 23.1" E | | Hadleigh | 52° 2' 34.5" | 0° 57' 0.7" E | | Lindsey | 52° 5' 40.5" | 0° 52' 58.9" E | | Newton | 52° 2' 9.1" | 0° 47' 47.4" E | | Groton | 52° 2' 23.6" | 0° 32' 21.1" E | | Waldingfield | 52° 3' 35.1" | 0° 47' 13.7" E | | Acton | 52° 3' 31.2" | 0° 45' 31.7" E | | Beauchamp | 52° 3' 34.4" | 0° 37' 20.2" E | | Hedingham Castle | 51° 59' 35.6" | 0° 36' 7.6" E | | Ridgewell | 52° 2' 18.8" | 0° 32' 12.1" E | | Langham | 51° 57' 51.6" | 0° 57' 28.1" E | | Earles Colne | 51° 55' 34.2" | 0° 42' 15.6" E | | West Bergholt | 51° 55' 0.1" | 0° 50' 13.3" E | | Braxted | 51° 48' 25.5" | 0° 40' 58.4" E | | Kelvedon | 51° 50' 55.5" | 0° 41' 33.0" E | | Messing | 51° 50' 12.5" | 0° 45' 2.5" E | | East Thorp | 51° 51' 33.2" | 0° 46' 28.4" E | | Witham | 51° 53' 34.4" | 0° 38' 6.1" E | | Tarling | 51° 48' 13.0" | 0° 34' 11.7" E | | Willingale Spain | 51° 44' 31.6" | 0° 18' 40.0" E | | Braintree | 51° 52' 33.7" | 0° 32' 57.5" E | | Felstead | 51° 51' 23.3" | 0° 25' 59.2" E | | Great Leigh | 51° 48' 41.8" | 0° 31' 7.8" E | | Great Baddow | 51° 42' 55.8" | 0° 30' 7.2" E | | Chelmsford | 51° 44' 5.8" | 0° 28' 19.7" E | | Whittle | 51° 43' 43.4" | 0° 25' 39.6" E | | Roxwell | 51° 45' 2.3" | 0° 22' 57.7" E | | White Roding | 51° 47' 48.2" | 0° 15' 50.8" E | | Doddinghurst | 51° 40' 1.8" | 0° 17' 49.4" E | | Theydon Mount | 51° 40' 18.0" | 0° 9' 31.1" E | | Navestock Mill | 51° 38' 52.2" | 0° 15' 55.8" E | | Theydon Garnon | 51° 40' 23.6" | 0° 7' 44.2" E | | Havering | 51° 36' 58.7" | 0° 11' 6.1" E | | Names of stations | Latitudes | Longitudes | |------------------|-----------|------------| | Cupola at Woodford | 51° 36' 26.5" | 0° 12' 3.1" E | | Ruins near Ilford | 51° 34' 17.3" | 0° 3' 30.7" E | | Hunsdon | 51° 47' 40.8" | 0° 3' 23.5" E | | Broxbourn | 51° 44' 30.8" | 0° 47' 8.8" E | | Harlow | 51° 46' 54.4" | 0° 5' 38.4" E | | Sabbridgeworth | 51° 48' 42.5" | 0° 9' 14.4" E | | Bishop Stortford | 51° 52' 13.4" | 0° 9' 30.5" E | | Stanstead Mount-fitchet | 51° 53' 40.2" | 0° 12' 35.1" E | | Farnham | 51° 54' 4.4" | 0° 9' 7.0" E | | Windmill, Meesdon | 51° 58' 18.5" | 0° 5' 4.9" E | | Newport | 31° 59' 2.5" | 0° 12' 50.6" E | | Shudy Camps | 52° 4' 24.2" | 0° 21' 49.9" E | | Ashdon | 52° 2' 54.7" | 0° 18' 17.6" E | **West Parts of Kent** | Names of stations | Latitudes | Longitudes | |------------------|-----------|------------| | Windmill, Seven-oaks | 51° 14' 58.5" | 0° 11' 12.9" E | | Chiddingstone Station, Mount Sion | 51° 11' 10.6" | 0° 8' 49.6" E | | East Peckham | 51° 14' 40.1" | 0° 22' 45.2" E | | Tudeley | 51° 11' 6.0" | 0° 19' 9.4" E | | Seal Chart | 51° 16' 13.6" | 0° 15' 35.3" E | | Tunbridge | 51° 11' 51.6" | 0° 17' 1.6" E | | Otford Mount | 51° 18' 55.3" | 0° 12' 25.3" E | | Well Hill | 51° 21' 9.8" | 0° 8' 55.3" E | | Crayford | 51° 27' 17.8" | 0° 10' 32.2" E | | Ash | 51° 21' 26.9" | 0° 18' 0.2" E | | Bidborough | 51° 10' 0.3" | 0° 14' 6.8" E | | Station near Bidborough Church | 51° 10' 4.0" | 0° 13' 44.3" E | | Tree near Kibben's Cross | 51° 7' 48.8" | 0° 21' 45.1" E | | Cowden Steeple | 51° 7' 34.2" | 0° 6' 9.9" E | | Leigh Steeple | 51° 11' 51.8" | 0° 12' 58.3" E | | Ide Hill | 51° 14' 40.3" | 0° 7' 43.9" E | | Eatonbridge | 51° 10' 6.0" | 0° 4' 3.3" E | | Hadlow | 51° 13' 23.4" | 0° 20' 22.3" E | | Sundrich | 51° 16' 27.7" | 0° 8' 8.7" E | | Windmill, Ketson Common | 51° 22' 27.5" | 0° 1' 59.6" E | | Hayes Common | 51° 21' 46.9" | 0° 1' 35.3" E | | Flagstaff | | | | Names of stations | Latitudes | Longitudes | |-----------------------------------|-----------|------------| | Addington Common Flagstaff | 51° 21' 30.1" | 3° 6.6 E | | Farnborough | 51° 21' 20.4" | 5° 53.2 E | | St. Mary's Cray | 51° 23' 42.9" | 6° 57.3 E | | Halstead | 51° 19' 57.3" | 7° 43.6 E | | Bromley | 51° 24' 17.8" | 5° 19.9 E | | Hayes | 51° 22' 41.3" | 1° 9.8 E | | Lewisham | 51° 27' 20.2" | 5° 27.7 W | | Station, New Cross | 51° 28' 5.1" | 2° 29.3 W | | Eastcombe Point | 51° 29' 52.2" | 1° 3 E | | Woolwich | 51° 29' 34.6" | 3° 38.2 E | | Bexley | 51° 26' 24.8" | 9° 17.3 E | | Charlton Farm | 51° 23' 27.0" | 4° 10.9 E | | Dartford Brent Mill | 51° 26' 26.1" | 14° 10.5 E | | Hartley | 51° 22' 34.5" | 19° 2.3 E | | Ridley | 51° 21' 4.9" | 19° 13.3 E | | Cliff Steeple | 51° 27' 43.1" | 29° 50.2 E | | Gravesend Steeple | 51° 27' 39.2" | 22° 9.7 E | | Chalk Steeple | 51° 25' 35.4" | 25° 11.5 E | | Guard Room, Lower Hope Point | 51° 28' 55.3" | 28° 8.6 E | | Flagstaff, Tilbury Fort | 51° 27' 8.8" | 22° 37.4 E | | Names of stations | Latitudes | Longitudes | |-----------------------------------|-----------|------------| | Rainham | 51° 21' 46.5" | 36° 30.7 E | | Southfleet | 51° 24' 59.4" | 19° 10.7 E | | Shorn Mill | 51° 24' 54.7" | 25° 41.3 E | | Gillingham | 51° 23' 27.4" | 37° 3.0 E | | St. James's, Isle of Grain | 51° 27' 36.9" | 54° 6.9 E | | Friendsbury | 51° 25' 29.0" | 30° 18.4 E | | Star Inn | 51° 22' 18.5" | 37° 1.1 E | | Upper Bell Inn | 51° 19' 49.2" | 30° 28.9 E | | Upchurch | 51° 22' 35.1" | 38° 49.2 E | | Bobbing | 51° 21' 13.6" | 42° 34.0 E | | Frinstead | 51° 17' 3.9" | 42° 37.9 E | | Hern Hill | 51° 18' 28.2" | 57° 34.9 E | | Stockbury | 51° 19' 27.6" | 38° 55.3 E | | Hucking | 51° 17' 37.6" | 38° 38.3 E | | East Church | 51° 24' 8.8" | 51° 31.9 E | | Milton | 51° 21' 20.3" | 44° 21.0 E | | Iwade | 51° 23' 39.5" | 43° 24.4 E | | Witchling | 51° 16' 8.4" | 44° 36.8 E | | Sheldwich | 51° 16' 31.6" | 52° 51.4 E | | Queenborough | 51° 25' 3.4" | 44° 36.5 E | | St. Mary's | 51° 27' 34.4" | 53° 40.1 E | | Feversham | 51° 19' 2.3" | 53° 35.7 E | In page 399, line 13, for G, read g. — 415, lines 5 and 6 from the bottom, for 430 revolutions, read 436. — 468, line 3, for 45 divisions, read 45. GENERAL VIEW of the ZENITH SECTOR. ELEVATION of the Side of the Interior FRAME carrying the T Side of the Interior FRAME carrying the ZENITH SECTOR. Top of the External Stand. Bottom of the Internal Frame resting on the Azimuth Circle.