257 



riicidence. 



40' 

 50 

 60 

 70 



80 

 85 

 90 



The results of experiment are generally in excess. This may bo 

 diio to the impossibility of obtaining rays of heat quite parallel from 

 terrestrial sources. To avoid this and other difficulties, experiments 

 have recently been made in Germany by M. Knoblauch, and in Paris 

 by MM. Provostaye and Depains. The results of the last named 

 observers are very conclusive in favour of the accuracy of Fresnel's 

 law. Their memoir had not reached the author of this paper until 

 his calculations were almost completed. 



3. On the solution of certain DiflFerential Equations. By 

 Professor Kelland. 



Until recently, general solutions of several classes of equations, 

 such as that which occurs in the theory of the figure of the earth, 

 could not be arrived at. An ingenious transformation lately ren- 

 dered it a matter of comparative ease to arrive at a solution of these 

 equations in those forms in which they are presented in the solution 

 of physical problems ; but still much remains to be done. The ob- 

 ject of the present paper is to supply some portion of the deficiency 

 in this respect, by the introduction of a new transformation, and the 

 adoption of the function r. The solutions thus obtained are perfectly 

 general, and are arrived at with the greatest facility. 



The Most Xoble the Makquis of Tweeddale 

 was duly elected an Ordinary Fellow. 



The following Donations to the Library were announced : — 



The Astronomical Journal. Vol. I., No. 1. 4to. — By the Editor. 



Athenaeum — Annual lleport — General Abstract of Accounts from 



1st January to 31st December 1848. 8vo. — Bi/ the Athe- 



