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ACCOUNT OF THE PROCEEDINGS OF THE ROYAL SOCIETY. 



interchanges of heat on either side are equal : and this 

 theory has been adopted by Professor Pictei, and by other 

 philosophers. Hence the author endeavours to deduce the 

 law already inferred from Richmann's experiments. Mr. 

 Prevost observes, that this theory virould be equally applicable 

 to the opinion of those who consider heat as consisting in 

 the undulations of an elastic medium; although he thinks 

 that opinion liable to many objections,e specially on account 

 of the resistance which the motions of the planets must suffer 

 from it. In a note added by Dr, Youn^, who communi- 



cated the paper, the assertion of Newton is quoted iii 

 answer to this objection, yet Dr. Young confesses that 

 Newton appears to have calculated erroneously : but he ob- 

 serves, that if the slightest difficulty of this kind should occur 

 from astronomical considerations, it might be avoided by 

 considering the luminiferous ether as unconcerned in the 

 phenomena of cohesion, and then its rarity might be as- 

 sumed as great as we chose to make it. 

 The Society adjourned to November 4. 



