148 Astronomical and Nautical Collections. 



... 5_ , , — Aii 3 */zdz 



refraction; thus, if y ~ z-, we nave cl.r = - — — 



mz 2 mz 



and S — x — 1 = — (1 — s/z), whence dr fa — i— 1 



m V C 2s ~ 2 P%) 



= , . ZLJL ^^ , or, if V * = +> 



"v \ m m J 

 ~~ Pr y ) an( j tj ie fluxion assumes the 



y/ \m m J 



form — , Article Fluents, n. 259; and there 



*J (a+bx + c.c-) 



is little doubt that such a hypothesis, if advanced with sufficient 

 pomp and ceremony, would be allowed to represent the consti- 

 tution of the lower parts of the atmosphere, which are princi- 

 pally concerned in the refraction, much better than that of 

 Bessel, though, perhaps, not quite so accurately as they might 

 be represented by a more appropriate, though less convenient, 

 exponent. 



London, 6th Aug. 1823. 



ii. Catalogue of the Orbits of all the Comets hitherto computed. 

 By Dr. Olbers and Professor Schumacher. Astr. Abh. I. 



" This Table originated from a request of the Editor of the 

 Astronomical and Nautical Collections, that Dr. Olbers would 

 have the kindness to furnish him with any additional materials 

 that could be incorporated with the former Table, as it stood at 

 the end of the Essay on Comets. He was so good as to send 

 his remarks to Professor Schumacher, who introduced them, in 

 their proper places, together with some corrections and ad 

 ditions of his own, into Delambre's Table." 



[The remainder, n. 71 . . 125, in our next Number.] 



