Observations Made at Chislehurst, in Kent, in the Year 1774. By the Rev. Francis Wollaston, LL.B. F. R. S.

XXVII. Observations made at Chislehurst, in Kent, in the Year 1774. By the Rev. Francis Wollaston, LL.B: F.R.S. HAVING now compleated my original design, and kept my clock going for a third year, without the least touch of the oil, or any alteration whatsoever, I presume the result of my observations to ascertain the rate of its going, may not be an unacceptable addition to the former papers on that subject, delivered to this Society. The regular difference between the summer and winter months, and some degree of similarity between those differences, seems to shew a regularity in the cause. What that may be, is not fully to be ascertained hereby; though it seems to have been difference of moisture, rather than of heat. By comparing these three last years with that which I first gave, when the clock was in some degree foul, it seems as if it were most affected when the work is clean. Yet is not that quite certain; for the differences, which decreasing gradually in the following table, would justify this conclusion, it may be observed, increase again in the last instance. The The first greatest loss was Dec. 1770 or — 1,9 " The next greatest gain June 1771 + 2,4 4,3 The next greatest loss Oct. 1771 — 1,9 4,3 The clock was cleaned November 1771, and might not be reckoned to get to any stated rate till the beginning of the next year; after which, | The first greatest loss was | Feb. 1772 or — 0,86 | |-----------------------------|---------------------| | The next greatest gain | July 1772 + 7,83 | | The next greatest loss | Jan. 1773 — 0,09 | | The next greatest gain | Aug. 1773 + 6,17 | | The next least gain | Feb. 1774 + 0,30 | | The next greatest gain | Aug. 1774 + 4,95 | | The next greatest loss to | Dec. 1774 — 0,90 | Hereby July and August appear to be the months for greatest acceleration, and January and February for retardation; contrary to the affection of metalline rods, but agreeable to the effect to be expected from moisture upon wood. Yet this difference is not so great in any degree, nor (what is more material to observation) by any means so sudden in its changes, as what is occasioned by heat upon metals. And even this, perhaps, might be obviated by a strong coat of varnish on the rod, or some preparation of the wood itself. One thing it may be proper to mention, as an accidental experience I have had the last year; that a clock so fixed, with a pendulum of so simple construction, is not easily affected by any tremulous motion of the building to which it is fastened. In the months of March, April, and part of May, I had occasion to make alterations in the top of my house, in order to gain more rooms in it; and notwithstanding the great jarring necessarily consequent upon taking off the old rafters, and laying on a new leaded roof, and new joists and floor over the observatory itself, the clock seems not to have been disordered at all by it. Between February 7th and 20th there will appear an error in the calculation of gain, to any one who shall take the trouble to examine it: not that I believe there is really any error in it; but by an accident in winding the clock (not having put down the spring sufficiently, which is intended to keep on the motion of the wheels,) there were 6" lost, as appeared by the assistant clock, which had been set with it just before. These 6" being allowed for, will reduce the loss of 2,1 to a gain of 3,9 in that interval of thirteen days, \[ -2,1 + 6 = +3,9. \] In the months of February, March, and April, I was frequently from home; so that the state of the thermometer and barometer, if I were to set them down, would be very imperfect. In the other months they are more compleat; yet there may, perhaps, in my absence, have been some days in them either higher or lower than what are here given. 1773. | Year | Month | Day | Clock + too fast. — too slow. for mean sol. time | Numb. of Days | Gain + or Loss — | Rate per Day | Throwing out | |------|-------|-----|-----------------------------------------------|--------------|-----------------|-------------|--------------| | 1773 | Dec. | 27 | Clock + 32° 19',7" | | | | | | | | | | | | | | | 1774 | Jan. | 3 | + 32° 26',9" | 7 | + 7,2 + 1,03 | 1 25 | 1 28 | | | Feb. | 7 | + 32° 41',7" | 35 | + 14,8 + 0,42 | 1 27 | 1 29 | | | | | Loss in winding 6" | 13 | + 3,9 + 0,30 | 1 35 | 1 38 | | | Mar. | 12 | + 32° 39',6" | 20 | + 6,0 + 0,30 | 1 28 | 1 31 | | | | 20 | + 32° 45',6" | 8 | + 2,4 + 0,30 | 1 40 | 1 43 | | | April | 2 | + 32° 53',1" | 13 | + 5,1 + 0,39 | 1 35 | 1 40 | | | May | 1 | + 33° 45',1" | 29 | + 52,0 + 1,79 | 1 36 | 1 40 | | | | 26 | + 34° 55',2" | 25 | + 70,1 + 2,80 | 1 40 | 1 43 | | | June | 8 | + 35° 40',6" | 13 | + 45,4 + 3,49 | 1 38 | 1 42 | | | | 22 | + 36° 30',5" | 14 | + 49,9 + 3,57 | 1 36 | 1 40 | | | July | 1 | + 37° 7',8" | 9 | + 37,3 + 4,14 | 1 36 | 1 40 | | | Augst | 1 | + 39° 22',5" | 31 | + 134,7 + 4,34 | 1 37 | 1 40 | | | | 19 | + 40° 49',4" | 18 | + 86,9 + 4,83 | | | | | Sept. | 3 | + 42° 3',7" | 15 | + 74,3 + 4,95 | 1 32 | 1 35 | | | | 12 | + 42° 37',0" | 9 | + 33,3 + 4,70 | 1 35 | 1 38 | | | Oct. | 3 | + 43° 45',3" | 21 | + 68,3 + 3,25 | 1 35 | 1 38 | | | | 15 | + 44° 9',2" | 12 | + 23,9 + 1,99 | 1 33 | 1 36 | | | | 29 | + 44° 37',9" | 14 | + 28,7 + 2,05 | 1 30 | 1 33 | | | Nov. | 12 | + 45° 7',7" | 14 | + 29,8 + 2,11 | 1 30 | 1 33 | | | Dec. | 5 | + 45° 27',1" | 23 | + 19,4 + 0,84 | | | | | | 13 | + 45° 25',4" | 8 | — 1,7 — 0,21 | | | | | | 24 | + 45° 18',5" | 11 | — 6,9 — 0,63 | | | | 1775 | Jan. | 1 | + 45° 11',3" | 8 | — 7,2 — 0,90 | 1 20 | 1 23 | 1774 | Year | Thermometer without doors exposed to the North | Thermometer near the clock | Barometer on the ground floor | Hygrometer near the clock | |------|---------------------------------------------|---------------------------|-------------------------------|--------------------------| | | Hor. 8 A. M. | Hor. 2 P. M. | Hor. 11 P. M. | Hor. 9 A. M. | | | | 1774 | Jan. Highest | 48 | 50 | 48 | 47 | 29.85 | 70 | | | Lowest | 23.5 | 29 | 23 | 31 | 28.67 | 34 | | | May Highest | 60 | 67 | 53 | 57 | 29.98 | 23 | | | Lowest | 45 | 45.5 | 40 | 47 | 29.10 | 10 | | | June Highest | 70 | 74 | 60 | 65 | 30.11 | 20 | | | Lowest | 51 | 55 | 47 | 51 | 29.24 | 9 | | | July Highest | 72 | 82 | 60 | 65 | 30.14 | 19 | | | Lowest | 57 | 57 | 50 | 53 | 29.52 | 7 | | | August Highest | 70 | 76 | 63 | 65 | 30.12 | 34 | | | Lowest | 57 | 61 | 50 | 53 | 29.32 | 5 | | | Sept. Highest | 70 | 72 | 60 | 63 | 30.06 | 32 | | | Lowest | 49 | 51 | 46 | 51 | 29.915 | 11 | | | Oct. Highest | 56 | 64 | 54 | 55 | 30.37 | 27 | | | Lowest | 39 | 45 | 39 | 44 | 29.23 | 13 | | | Nov. Highest | 54 | 59 | 51 | 49 | 30.06 | 42 | | | Lowest | 31.5 | 33 | 31 | 34 | 29.02 | 20 | | | Dec. Highest | 50 | 53 | 51 | 45 | 30.54 | 70 | | | Lowest | 21 | 30.5 | 25 | 30 | 28.95 | 27 | Accidents of weather and various avocations have prevented me from making any other observations in the course of the last year; excepting the second disappearance of Saturn’s ring, and re-appearance of it again, both of which I was fortunate enough to observe. I had seen the ring many times after its first re-appearance; and observed it to be lessening again, till it was become but a mere a mere thread of light, Monday, April 4, though certainly visible then. Tuesday, April 5, the evening was very clear, yet no ring could I perceive with my $3\frac{1}{2}$ feet achromatic telescope; nor from that time did I see any thing of it (but, during part of the interval, the appearance of a dark belt across the planet,) till Thursday, June 30, when I thought I saw the preceding ansa. Saturday, July 2, I am sure I saw the whole ring again, as a thread of light; and as the preceding ansa, or end of that thread, appeared larger than the subsequent one, it probably was visible, and not only a deception, when I fancied I perceived it before. In these observations it deserves to be remarked, that the magnifying power of 100 seemed, from its brightness, to shew the thread of the ring more visibly than 150. Chislehurst, Jan. 1775. FRANCIS WOLLASTON.