1836.] 



Observations respecting Halleifs Comet. 



the side a. But as the arcs must be very small never ex- 

 ceeding two or three degrees they may be represented by 

 straight lines, therefore in the right angled plain triangle 



\ Tar,gA=-5- 



\ cos i A 



! A t =TangUxD. • 



Q. E. I. 



and to apply the values of the quantities before given. 



D = 58' If/ = 3496" log. == 3.54357 

 a= 1°58' 39"^ 7119" colog. = 6.14758 



9.691 15= Tang A=26°9'17 



Tang -J A = 13° 4' 38 y = 9.36602 

 D = 3.54357 



2.90959 = 812*= 13' 32". 



the same as before, while by this formula, logarithms to five 

 places are sufficient. 



20th October 1835. C. 



IX. — Observations respecting H alley's Comet. 



My Dear Sir, — It will be interesting to your readers to 

 learn that H alley's Comet is still visible through a telescope, 

 and it will probably so remain for twenty or thirty days to 

 come ; comparing the quantity of light which it at present 

 exhibits with that exhibited before the Peribelion passage it 

 would appear that it has lost no part of its brilliancy what- 

 ever by its approach to the Sun (a fact by the way which isS 

 at variance with the generally received opinion of astrono- 

 mers. 



We will now for a moment take a look at the past — the 

 Astronomer Halley, 150 years ago could have predicted 

 the present return of the Comet which so justly bears his 

 name to a conple of months ; but it is to the refined astro- 

 Homy of the present century to which so much honour and 



