346 PHILOSOPHICAL TRANSACTIONS. [aNNO 1687. 



SO stiled ; their instructions being, besides their spiritual function, to prosecute 

 the business of the Royal Academy of Paris, by accurately observing the curious 

 things in art and nature, and particularly to make observations for discovering 

 the longitudes of the places where they pass ; for which purpose they are well 

 provided with instruments. The varia'tion of the needle observed by them at 

 Siam, in l685, was 30 minutes west. And the longitude of that place, de- 

 duced from an observed eclipse of the moon, is 98° 30' east of Paris. 



Account of a Comet seen at Leipsic, Sept. 1686, taken from the Leipsic Acta 

 Eruditorum for the Month of Nov. 1686. N° 186, p. 256. 

 This comet was observed at Leipsic by Mr. Kirck ; in whose ephemerides 

 for this year there is likewise a brief account of it. He saw it only twice, viz. 

 on the 8th and Qth of September, O. S. 1686; and observed it as follows. 

 Sept. 8, 4h. morn, about day-break, he found the comet in the constellaiion of 

 Leo, to the right hand of the Lucida in Lumbis ^, and resembling that star 

 in colour and magnitude, with a thin and short tail, extended upwards. Over 

 the comet, in the same vertical, was the star fi S^ of Bayer, or 21 Tychoni, 

 exactly l° distant from it, by the micrometer ; and a line drawn from the Lucida 

 in Lumbis ^, to the comet, passed about half a degree to the right hand of the 

 said 6 Leonis. The distance of the comet from Regulus, taken by a radius, 

 was about 17°. The next morning, Sept. 9, the comet appeared again obscurer, 

 and more difficult to observe, than before, on account of the day-light : how- 

 ever, at 3h. 58m. its distance from 9 ^ was found by the micrometer 2° 23'^, 

 and at 4h. 40m. again 2° 25-1-. To verify the times, the altitude of the Lucida 

 in Lumbis ^ was observed 1 1° 10' at 4h. 8m. morn. A right line drawn by the 

 comet and the said 9 Leonis, towards (3 Leonis, or the Lucida Colli, left that star 

 a little to the right hand. The following days being cloudy, no more could be 

 observed. ^ ' 



This comet was seen by a countryman, who first gave notice thereof, from 

 the 6th to the 12th of September; the result of whose observations is, that the 

 comet was direct in motion, that it moved about l^ degree per diem, and that 

 it seemed rather to decrease in latitude. On the 7 th of Sept. it was about 24' 

 distant from 9 Leonis. 



This star 9 Leonis, was then in 9° 2' of tllj, with north latitude 9° 4]%. 

 Whence at the time of the first observation it may be concluded that the 

 comet was in 9° 55' of Ti)j, with north latitude 9° 15'. And at the second ob- 

 servation the longitude of the comet will be found about 11° 20' in n)^, with 

 nearly the same north latitude as before. 



