Geological Society '. Anniversary Address, \M2. 541 



sulphuric acid being converted into bisiilphate, while the other 

 portion is diluted by the displaced water of the first portion, 

 and thus heat evolved. 



On performing the direct experiment, which M. Hess ap- 

 pears to have neglected, using a saturated solution of sulphate 

 of ammonia, and sulphuric acid of specific gravity 1*256, I 

 obtained, on mixing, S'-i" of cold instead of any heat. But 

 on diluting the sulphate of ammonia with a volume of water 

 equal to that of the dilute acid, a fall of 1"12° occurred. De- 

 ducting this from the former, there remains a fall of 3*88° due 

 to the combination of the two salts, sulphate of water with 

 sulphate of ammonia. But this may be explained. The bi- 

 sulphate of ammonia formed is an anhydrous salt, unlike the 

 double sulphate of magnesia and ammonia, which carries along 

 with it all the water of crystallization of the sulphate of mag- 

 nesia. But the sulphate of water itself, as it exists in diluted 

 sulphuric acid, is a largely hydrated salt, like sulphate of mag- 

 nesia. The water of the former, on being set free in the last 

 experiment, absorbs heat, because heat was evolved originally 

 in the combining of this water with the sulphuric acid. 



Although certain small corrections on these experiments 

 for changes in capacity for heat of the liquids have been 

 neglected, yet they are sufficient to demonstrate that no heat 

 is evolved in the formation of double sulphates, and also, as 

 appears by the last experiment, that these compounds are 

 formed at once on mixing the solutions of their constituent 

 salts, whether precipitation occurs or not. Sulphate of potash 

 and water are therefore equivalent in the constitution of such 

 salts, or equi-calorous, if a term may be coined to express this 

 relation. 



LXXX. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY. 



Address delivered at the Anniversary Meeting on the 1 ^th of Fe- 

 hrtuinj 1842 ; and the announcement of the Aivard oftJie Wollaston 

 Medal and Donation Fund for the same Year. By Roderick 

 Impey Murchison, F.R.S., President of tlie Society, 



AWARD OF THE WOLLASTON MEDAL AND DONATION FUND. OB- 

 SERVATIONS BY THE PRESIDENT. 



THE Wollaston Medal has been this year awarded to M.Leopold 

 von Buch, for "the eminent services lie has rendered to Geology 

 by his extraordinary and unremitting (ixertions during a long scries 

 of years, and for his recent researches in l^alaeontology." 



Since geology has been a science no individual has more success- 

 fully appiied a powerful mind to its cultivation, or more liberally ex- 



