m 



of ammonia, liquefies when heated, being more fusible and less vola- 

 tile than the ingredients separately, and concretes into a gray cry- 

 stalline mass on cooling. The author then describes the property of 

 several solutions of corrosive sublimate and sal-ammoniac, showing 

 that the solubility of the compound salt exceeds that of the most so- 

 luble ingredient ; and details some experiments illustrating the action 

 of the muriates of baryta, magnesia, potash, and soda, upon corro- 

 sive sublimate. 



On the State of Water and Aeriform Matter in Cavities found in cer- 

 tain Crystals. By Sir Humphry Davy, Bart. P.R.S. Read June 

 13, 1822. [Phil. Trans. 1822, p. 367.] 



After adverting to the interesting phenomena connected with cer- 

 tain crystalline products of the globe, and showing that the Huttonian 

 theory more plausibly accounts for their formation than the Wer- 

 nerian, Sir Humphry proceeds to offer additional arguments in its 

 favour, deduced from his examination of the aeriform and liquid 

 matter contained in certain siliceous stones. The fluid was in all 

 cases found to be nearly pure water ; and the elastic fluid was pure 

 azote, existing always, however, in a state of considerable rarefac- 

 tion; namely, from 12 to 18 times more rare than atmospheric air. 

 In the only two cases in which the relation of the bulk of the water 

 to that of the void space could be ascertained, it was nearly as 2 

 to 1. 



In the chalcedonies of basaltic rocks the gas was also azote, but it 

 was 61 or 70 times more rare than atmospheric air, the quantity of 

 water to that of void space being the same as in the rock crystal. 



It occurred to the author that atmospheric air might have been 

 originally included, and that the oxygen might have been absorbed 

 by the water ; and an experiment is detailed, the result of which 

 proved favourable to such an opinion. None of the crystals of se- 

 condary rocks examined by Sir Humphry Davy were impervious to 

 air ; in these, therefore, atmospheric air was found of its usual den- 

 sity ; this was even the case with the cavities in dense calcareous 

 spar. 



The President observes, in conclusion, that it appears difficult to 

 explain the results obtained, unless by supposing the water and silica 

 separated from each other at a very high temperature ; at such tem- 

 peratures a liquid hydrate of silica might exist under pressure, and 

 like other liquid bodies in the atmosphere, it would probably contain 

 small quantities of atmospheric air ; and upon such a supposition, the 

 phenomena presented by the water in rock crystal and chalcedony 

 might be accounted for. 



