462 Proceedings of Philosophical Societies. [June, 



sion of the temperatures ; but the great liberation of latent heat 

 by compression, and its absorption by expansion, seem to render 

 the mechanical application of them at temperatures greatly 

 elevated above the boiling points of the respective liquids of 

 doubtful economy. No doubt, however, in this respect, observed 

 the President, can be entertained of those vapours which can 

 only be produced under high pressures, and at common temper- 

 atures. To illustrate this subject, Sir Humphry described the 

 results of some experiments on the increase of elastic force in 

 the vapours of several of the condensed gases ; one of them, 

 that of liquid sulphuretted hydrogen, which exerts a pressure 

 of 14 atmospheres at 3°, becomes equal in pressure to 17 atmo- 

 spheres at 47°. 



Among other experiments described in this communication, 

 were some in which the author had liquefied prussic gas and 

 sulphurous acid gas, by confining them with a portion of ether 

 in glass tubes over mercury, and then raising the ether in 

 vapour: — as this vapour condensed, the liquefied gas resumed 

 its aeriform state, and cold was produced. 



Sir Humphry concluded with some remarks on the probable 

 applications in the arts of the condensed gases ; among which, 

 besides their employment as mechanical agents, he suggested 

 those of impregnating water with large quantities of carbonic 

 acid and other gases, without the aid of mechanical pressure ; 

 and the ready production of cold, in consequence of the rapidity 

 with which they evaporate. 



At this meeting a paper was also read, On the Temperature, 

 at considerable Depths, of Fresh-water Lakes, within the Tropics. 

 By Cant. Edward Sabine, FRS. in a letter to the President. 



Sir H. Davy had requested Capt. Sabine, while engaged in 

 his late observations in the tropical regions, to make some expe- 

 riments on the temperature of deep lakes, with a view of obtain- 

 ing facts in illustration of that interesting object of inquiry, the 

 temperature of the interior of the earth ; no opportunity of insti- 

 tuting such researches had, however, occurred to him, but he 

 had made one experiment on the subject, in a part of the Carib- 

 bean Sea, which, from its confined situation, nearly resembled a 

 lake ; and this experiment he proceeded to describe, from the 

 original memorandums of it. 



At the period of this experiment, Capt. Sabine was on board 

 one of his Majesty's vessels, in lal. 20° 30' N. and long. 83° 30' 

 W. ; between the Caymans, and Cape St. Antonio, in the Island 

 of Cuba. The weather was fine, with light airs, and the sea not 

 swelling in a great degree. To the bottom of a line of above 

 1200 fathoms, a strong iron cylinder was fastened, the top of 

 which screwed down upon leather in order to prevent the entrance 

 of the water, by the compression of which in the cylinder the 

 temperature might be raised : within the cylinder was a Six's 

 self-registering thermometer, prevented, by means of springs 



