An Account of Some Eclipses of the Sun and Moon, Observed by Mr Tho. Brattle, at Cambridge, about Four Miles from Boston in New-England, Whence the Difference of Longitude between Cambridge and London is Determin'd, from an Observation Made of One of Them at London. By J. Hodgson

open Cistern of the other. The Parts thus dispos'd, and the Stop-cock being turn'd, the Condens'd Air proceeds strongly thro' the Swan-neck Pipe, which discharges it into the Horizontal Tube G. Whose Currency so lessens the Pressure of the Atmosphere upon the Cisterns of the respective Barometers as to cause the Mercury to descend 2 inches at least. And 'tis observable, That that Barometer which is 3 foot distant from the Current Air is equally affected, and subsides parallel with the other. Likewise it is to be noted, that as the Current Air is weakened in its force, so doth the Weight of the Atmosphere again Encrease, and the Mercury in the Barometers gradually Ascend. III. An Account of some Eclipses of the Sun and Moon, observed by Mr Tho. Brattle, at Cambridge, about four miles from Boston in New-England, whence the Difference of Longitude between Cambridge and London is determin'd, from an Observation made of one of them at London. By J. Hodgson. On the 12th of June 1694, in the morning I went to the Colledge at Cambridge, about 4 miles from Boston, and observed, with the Brass Quadrant there, with Telescopick Sights, the Rays of the Sun being transmitted through one of the said Sights, on a clean Paper, pasted on a plain piece of Board, and fastned at right angles at about a foot distance from the said Sight, on which Paper I had drawn a Circle between 2 and 3 Inches Diameter equal to the Suns disk, and within that several Concentrick Circles dividing the Diameter into 24 equal equal parts, whereby I could observe to \( \frac{1}{2} \) a digit, the room in which the Observation was made was darkened with Blankets, and in order to render the Observation the more Exact (Mr Henry Newman assiting me all the while) I took the Altitude of the Sun with the aforesaid Quadrant, as followeth. Observations made of the Suns Altitude before the Eclipse began, in order to rectifie the Watch. | By the Watch | Comp. Altit. Time by Calcul. differ. | |--------------|-------------------------------------| | h | | | at | | | 8 26 37 | 49 31 | | 31 27 | Mane 48 26 | | 38 26 | 47 20 | | | 8 16 40 | | | 21 40 | | | 28 32 | | | 9 57 | | | 9 47 | | | 9 54 | The Eclipse was first perceiv'd at 9 25 by the Watch, at which time the Sun had scarcely been eclips'd 1 minute, so that | By the Watch | True time. | |--------------|------------| | h | h | | 9 24 | 9 14 | It began | | 9 32 | 9 22 | about 1 digit eclipsed | | 9 48 | 9 38 | full 3 digits | | 9 57\(\frac{1}{4}\) | 9 48 | about 4 | | 10 06 | 9 56 | near 5 | | 10 15 | 10 05 | full 6 | | 10 33 | 10 23 | about 8 | | At | | | 10 43 | 10 33 | full 9 | | 10 47 | 10 37 | full 9\(\frac{1}{2}\) | | 10 53 | 10 43 | full 10 | | 10 59 | 10 49 | about 10\(\frac{1}{2}\) | | 11 03 | 10 53 | better than 10\(\frac{1}{2}\) | | 11 06 | 10 56 | much the same | | 11 09 | 10 59 | rather decreasing | By By the Watch True time 11 10 ½ 11 00 ½ sensibly decreased near 11 14 ½ 11 04 ½ ¼ of a digit 11 25 11 15 nearest to 10 digits full 9 digits, i.e. full 3 3 digits restored, or the Shadow rather within 9 digits At 11 29 11 19 8 ½ compleat 11 34 11 24 full 8 digits 11 44 11 34 full 7 11 48 11 38 full 6 ½ digits 11 52 11 42 just 6 0 02 P.M. 11 52 just 5 0 13 0 03 P.M. full 4 0 26 0 16 full 2 ½ 0 32 0 22 better than 2 0 41 0 31 better than 1 0 48 0 38 ended. Observations made after the Eclipse was done, of the Sun's Altitude, in order to rectify the Watch. Time by the Watch Comp. Altit. True time. differ. h 3 31 30 45 52 3 21 36 9 54 36 15 46 23 26 16 9 59 38 10 P.M. 46 45 28 16 9 54 46 50 48 19 36 48 10 02 48 10 48 30 38 20 9 50 Hence it appears, that the Watch went about 10 minutes too fast during the whole Eclipse, as we have all the way allowed. So So that the Eclipse Began at 9 14 Mane. Ended at 0 38 P. M. Lasting in all 3 24. Note, that in the Calculation, the Latitude of Boston was allowed to be 42° 2'5. The second is of a Lunar Eclipse, that happen'd Feb. the 11th, 1700, in the evening, as follows. The Moon rose eclipsed, and the Horizon was so overcast, that I dispair'd of having any observation; but at an hour past 6 she came from under the Cloud, and at 6 h 25' I had just a sight of her, and judge her eclips'd about 5 digits, at 6 29 The Section equidistant from M. Ætna & Horminius. 32 Palus Maræotis begins to be seen. 34 ½ Palus Maræotis and Mons Apollonius ½ out. 37 ½ Palus Maræotis quite free, and Palus Maræotis and Palus Maeotis in the perpendicular. 42 ¾ The Shadow near an Inch from Palus Maræotis, Mons Horminius and Mons Hercules. 46 ¼ Palus Maræotis in the Nadir, and that part of Palus Maeotis to my right hand in the Prime Vertical. 57 The upper part of the Section is now, and has been for a long time in Insula Major in Mare Caspio (and the Section now perpendicular) and the lower part wheeling about from Palus Maræotis. 7 20 Mount Sinai first appears at 22' wholly free. 25 ½ Palus Maræotis and Mons Horminius near perpendicular. 43 The Eclipse over in the Telescope, and at 49 to to the naked Eye. My Clock was set by my Ring-Dial about 9 a Clock in the morning, as exactly as I could judge, and the ob- Y y y y y y y y y y y y Observation was made with my 4½ foot Telescope, with all four Glasses in it. The Observation of the Eclipse of the Sun on the 27th of November 1703, was as follows. At half an hour past 8 in the morning, I set my Clock exactly by my Ring-Dial, and at half an hour past 9 they nicely agreed, at 10 00 The Sun was not touch'd. 06 The Moon enter'd on the SSW Point as near as I could judge. 15 The Eclipse was considerably advanc'd. 20 seem'd to be about half a digit eclipsed, rather more than less, and the Section to be a small matter more Westwardly. 10 25 Much the same, and near the same point. 30 seem'd to be less. 33½ The middle of the Section nearer the SW, and the Diameter of the Section less every way. 37½ Much less and nearer the West. 44½ It ended, and was just over, going off near the SW, so that all the while it was within a point or two of the place where it first came on, or between the SSW and the SW. I judg'd when it was at the height, that the Chord of the eclipsed part was nearest equal to the side of an inscrib'd Decagon, or subtended about ¼ of the Periphery of the Sun's Disk. I observ'd this Eclipse with a Telescope of one joint, 4 foot and a half in length, and had only 2 Glasses, so that it inverted the object; and I had a red Glass which suited it, so that I could screw it in just before the Eye-Glass, and was not fain to hold it in my hand, as when I ob- I observ'd the Sun's Altitude with the brass Quadrant, which was a great convenience. The last is an Observation of the Eclipse of the Moon on December the 12, 1703 in the morning. Time by the Clock. h 11 45 That part of the Moon's Disk near Alabastrinus looks somewhat duskish, and the Eclipse beginning to enter between Palus Maræotis and M. Porphyritis. 11 53 The true Shadow was well entred. 58 M. Porphyritis just cover'd. 12 03 near 3 digits darkened. 7 Mount Ætna begins. 9 quite covered. 14 Lacus Niger major and M. Sinai almost equidistant from the Section of the Shadow, Lacus Niger Major, being somewhat the nearer of the two. 18 Lacus Niger Major begins 19 quite covered. 21 Mount Sinai begins. 21 Quite covered and the Moon about 6 digits eclipsed. 12 24 Besbicus begins. 26 Quite covered. 28 Byzantium begins. 29 Covered and Mount Horminius begins. 32 Apollonia begins. 33 Covered. 37 The Shadow equidistant from M. Corax and Mount Paropamisus, or somewhat nearer to Mr Corax. 39 between 9 and 10 digits eclipsed. 43 M. Corax begins. Y y y y y y y y y 2 Palus Maeotis begins, and at 45° the inner of M. Paropamisus begins. Palus Maeotis quite covered. The Moon not quite eclipsed. Nor yet. Nor yet. Scarce. Quite Immerg'd and the Moræ begins. Precisely she Emerg'd between Palus Maræotis and Mons Porphyritis. Palus Maræotis begins. Quite clear. M. Porphyritis quite clear. About 3 digits restor'd. Mount Ætna begins. That and Lacus Niger Major at the same time clear. Mount Sinai about half free. Quite free, and about 6 digits restored. Besbicus free Bysantium free. About 9 digits seem'd to be restor'd. Mons Herculis free. Palus Maeotis begins. Quite free. Insula Major in Mare Caspio free, and in the middle of the Section. Not yet wholly clear. Fully over in the Telescope, tho a kind of a Smoak remained some little after to the naked eye. In order to the adjusting of the time, I set my Clock with the greatest exactness I could the morning preceding, both from my Ring-Dial and the rising of the Sun, which I very narrowly watch'd and observed, and found it to agree agree with the Sun's setting the following evening; so that it went all the time the Eclipse was, very steadily and regularly; but for the greater Certainty and Satisfaction, I took the Altitudes of the following Stars with the Brass Quadrant with Telescope Sights out of my Chamber Window, the lowness whereof would not permit me to take them, when they were at all higher elevated. *in dextro humero Orionis.* By the Watch Comp. Alt. Differ. | h | h | " | " | |---|---|---|---| | 6 | 15 | 78 | 18 | | 6 | 21½ | 77 | 03 | | 26½ | 76 | 11 | Procyon | h | h | " | " | |---|---|---|---| | 8 | 9½ | 77 | 20 | | 14½ | 76 | 20 | | 21 | 75 | 13 | Re- | h | h | " | " | |---|---|---|---| | 10 | 8½ | 77 | 46 | gulus | h | h | " | " | |---|---|---|---| | 17½ | 76 | 11 | This is all the account that can be given at present, by Sir, Your Humble Servant, T. B I had the good fortune (by the assistance of some ingenious Friends in Finch-Lane, near the Exchange) to make some few observations of the last, of December the 11th, 1704 (of which I gave an account to this Honourable Society some time since) as follows. The Heavens being cloudy most part of the night, it was 35' after 4 in the morning following, before I could could perceive that the Moon was eclipsed, and then as near as I could judge, she had been so about 3 or 4 minutes at most, from whence we may conclude it began at London about 31 or 32 minutes after 4 the same morning. Mr Brattle found, that at 44 minutes after 11 at Night, part of the Moon's Disk look'd somewhat duskish, and that at 52 minutes, the Shadow was well entred, so that from hence, as well as from a Comparison of the Ingress and Egress of the principal Spots, it probably began there about 49 minutes after 11, whence it follows, that Cambridge in New England lies 4° 4' 2½, or 70° 37' to the Westward of the Meridian of London. I happen'd to see the Moon the same morning at 35 minutes after 5, when she wanted at most but 3 minutes of being totally eclipsed; so that at London she immerg'd at 38 minutes past 5. Mr Brattle saw her immerge exactly at 54 minutes after 12, whence it follows, that the difference of the Meridians found by comparing these observations, is 4 h 43' ½, or 70° 52' agreeing very well with the former; so that by taking a mean between them, the difference of Longitude of the 2 Places is 4 h 43', or 70° 45'. I saw no more of the Eclipse that morning, and should be very glad to meet with some other observations to confirm these, but their mutual agreement gives great reason to believe that the Deductions are good, and may be rely'd upon.