1820.] Physical Science during the Year \%\d. 9 



perature of mines is higher than that of the air at the surface of 

 the earth where these mines exist. I think that a very satisfac- 

 tory explanation of this difference may be given without having 

 recourse to the notion of a subterranean or central fire ; but the 

 fact itself is undoubted, and furnishes an example of the hazard 

 which we run, if we venture to make general assertions respect- 

 ing heat without being at the trouble of subjecting our notions 

 to the test of experiment. Whoever wishes to see how far even 

 a man of great ingenuity may deviate from the truth, when he 

 proceeds in that manner, has only to peruse Boerhaave's treatise 

 on heat, in his System of Chemistry. 



I may mention here, though quite unconnected with the 

 preceding observations, the great heat which Dr. Clarke has 

 produced by his gas blow-pipe. He not only fused half an 

 dunce of platinum, but kept it, he says, in a boihng state before 

 his class. — (See Annals of Philosophy, xiv. 230.) 



IV. Galvanism. 



Dr. Hare, Professor of Chemistry in the Medical Department 

 of the University of Pennsylvania, has published (in a paper to 

 be found in the Annals of Philosophy, xiv. 176) a theory of 

 galvanism differing considerably from all those hitherto started. 

 According to him, the galvanic fluid is a compound of caloric 

 and electricity. The electricity is increased by the mmiber of 

 pairs of plates, and when this number is very great, as in Deluc's 

 column, the calorific effects become evanescent. The x^aloric is 

 evolved by the increase of the surface, and he has shov.'n that it 

 may be very intense when only a single pair of plates, or what is 

 equivalent to it, is used. He has given us the drawing of a 

 galvanic battery constructed on this principle, which produces 

 intense ignition without any electrical phenomena. 



As I have not yet had leisure to study the phenomena exhi- 

 bited by this new modification of the galvanic battery, I should 

 consider it as improper to make any remarks on Dr. Hare's 

 ingenious hypothesis at present. What I have to say on the 

 subject, therefore, I shall reserve for another opportunity. 



V. Supporters of Combustion. 



Nothing veiy important has been added to the facts previously 

 ascertained respecting these very important bodies. The follow- 

 ing are the only observations which I have been able to glean : 



1. Oxygen. — Soon after the discovery of this gas, and the 

 knowledge of its most remarkable properties, it was tried whether 

 when breathed instead of common air, it would not act medici- 

 nally, and in particular whether it might not in all probability 

 prove a remedy in consumption. The effects observed were 

 directly the contrary of what had been anticipated. The velo- 

 city of the pulse was accelerated, and the fatal effects of the 

 disease became more speedy. This led medical men not 



