401 



Table at about 83° 10'; is deficient by a second at about 

 84° 30'; and by I" at 85°. 



The second formula, which may be reduced to logarithmic 

 calculation by the equations, 



log tan 2 p = log tan + 2,81 296, } , . 



log R = log tan p + 3,24657, S ^ ^ 



does not agree quite so closely with Dr. Robinson's Table, 

 in the earlier part of it ; but the error, positive or negative, 

 seems never to exceed half a second, within the extent of 

 the Table, that is, as far as 85°. 



It appeared to Sir W. H. worth noticing, that the results 

 of such (necessarily) long and complex calculations, as those 

 which Dr. R. had made, could be so nearly represented by 

 formulae so simple : of which, indeed, the first is evidently 

 analogous to Bradley's well known form, but differs in its 

 coefficients. The second form is more unusual, and gives 

 (approximately) the mean refraction as a root of a quadi'atic 

 equation. It has been used (with other logarithms) by 

 Brinkley, for low altitudes. 



DONATIONS. 



Address to the Geological Society of London. By Rode- 

 rick J. Murcheson, F. R. S. A. Presented by the Author. 



Report of the Meeting of the British Association held at 

 Manchester in 1842. Presented by the Association. 



Statutes relating to the Admiralty, to the 8th of Geo. III. 

 Presented by Captain Portlock. 



Proceedings of the Glasgow Philosophical Society. 1841- 

 1842. Presented by the Society. 



Memoirs published by the Society of Sciences in Holland. 

 Vol. II. Second Series. 



Proceedings of the American Philosophical Society. Vol. 

 II. Parts 24 and 25, 



Transactions of the American Philosophical Society. Vol. 

 VIII. New series. Parts 2 and 3. Presented by the So- 

 ciety. 



