900 



sulphate group also, which have the same relation to each other as 

 the potasli saltf-. 



The relation of the salts of potash to those of soda, in times of 

 equal clifiusibility, appeared to be as the square root of 2 to the square 

 root of 3 ; which gives the relation in density of their diffusion mo- 

 lecules, as 2 to 3. Hydrate of potash and sulphate of magnesia were 

 less fully examined, but the first presented sensibly double the dif- 

 fusibility of sulphate of potash, and four times the diffusibiUty of the 

 sulphate of magnesia. If these times are all squared, the following 

 remarkable ratios are obtained for the densities of the diffusion mo- 

 lecules of these different salts, each of which is the type of a class of 

 salts, hydrate of potash 1, nitrate of potash 2, sulphate of potash 4, 

 sulphate of magnesia 16, with nitrate of soda 3 and sulphate of soda 6, 



In conclusion, it was observed, that it is these diffusion molecules 

 of the salts which are concerned in solubility, and not the Daltonian 

 atoms or equivalents of chemical combination; and the application 

 v,-as indicated of the knowledge of the diffusibilities of different sub- 

 stances to a proper study of endosmose. 



January 10, 1850. 



GEORGE REXXIE, Esq., Vice-President, Treasurer, in the Chair. 



The Right Rev. Tlie Lord Bishop of Alanchester was admitted 

 into the Society. 



The following papers were read : — ■ 



1. Experiments and Observations upon the Properties of Light." 

 By Lord Brougham, F.R.S. Sec. 



The author states that the optical inquiries of which he here 

 gives an account were conducted in the first instance under the most 

 favourable circumstances, arising from the climate of Provence, 

 where they were commenced, being peculiarly adapted to such 

 studies : he further states tliat he subsequently had the great benefit 

 of a most excellent set of instruments made by M. Soleil of Paris; 

 remarking, however, that this delicate apparatus is only required 

 for experiments of a kind to depend u]ion nice measurements, and 

 that all the principles which he has to note in this paper as the 

 result of his experiments can be made with the most simple appa- 

 ratus and without any difficulty or expense. His statement of the 

 results of his experiments is thrown into the form of definitions 

 and propositions, for the purpose of making it shorter and more 

 distinct, and of subjecting his doctrines to a fuller scrutiny. He 

 premises that he purposely avoids all arguments and suggestions 

 upon the two rival theories, the Newtonian or Atomic, and the L'n- 

 dulatory. 



The following are the author's Definitions and Propositions. 

 Defixitions. 



1. Flexion is the bending of the rays of light out of their course 

 in passing near bodies. 



