Page:Philosophical Transactions - Volume 054.pdf/213

 supposing that you Gentlemen have received it. The latitude of Selenginsk is 51$d$6′6″. I have settled the longitude to be 6$h$57′50″ from the Paris meridian. Some immersions of the first and second satellite of Jupiter have given me 6$h$57′15″, 6$h$57′20″, and 6$h$58′31″, by comparing the observations of Mr. Rumowski with the tables corrected upon the observations made at Paris and at the Cape, and estimating, as well as I was able, the different effects of the reflectors and telescopes. The 15th of July, Mr. Le Monnier observed the meridional transit of φ Sagittarii at 18$h$25′38″ $2⁄3$ of his clock, being at 76°00′45″ from the zenith. The preceding limb of the Moon passed at 18$h$38′28″ $1⁄2$, or at 11$h$01′40″ apparent time; when the center passed, the distance of the upper limb was at 75$d$52′00″ from the zenith; and the lower at 76$d$22′25″; the threads, which are 5″ thick, being entirely upon the Moon. σ Sagittarii had passed at 18$h$35′22″$1⁄2$, the distance from the zenith being 75$d$22′20″. I have observed at Rodriguez the immersion of σ Sagittarii at 14$h$01′28″$1⁄2$ apparent time, and Mr. Rumowski observed at Selenginsk the immersion of φ at 11$h$24′51″ apparent time. Upon comparing all these things together, I find the longitude of Selenginsk to be 6$h$57′21″$1⁄2$ East from Paris. But this goes upon the supposition that the error of the tables has been quite constant during near 7 hours, which cannot be warranted. Lastly, the observation of the eclipse of the Sun made at Selenginsk June 3; 1761, compared with the same observation made at Tobolsk and at Cajanebourg, determines the longitude of Selenginsk 5$h$16′41″$1⁄2$ East from Cajanebourg, and at 2$h$34′30″ East from Tobolsk, consequently 6$h$58′22″