586 Proceedings of Philosophical Societies, [May^ 



IMPERIAL INSTITUTE OF FRANCE. 



Account of the Labours of the French Institute for 1812. 



( Continued from IV. p. 316.) 



Physical Department. By M. Le Chev. Cuvier, Per- 

 petual Secretary. 



Physics and Chemistry, 



Every one knows that heat is one of the principal instru- 

 ments of chemistry^ and one of the greatest forces which act 

 in its phenomena. We may consider it in itself, in its effects, 

 and in its sources. 



Count Rumford, who is continually occupied with the 

 sciences, as far as they contribute to the good of society, has 

 this year treated of heat under this last point of view, and has 

 endeavoured with much care to determine how much heat is 

 produced by the combustion of each substance. 



To attain this object, it was necessary in the first place to 

 have a general method of measuring exactly these quantities of 

 heat ; and when we reflect on the complicated nature of the 

 phenomena of combustion, we must be sensible of the numerous 

 difficulties which Count Rumford had to encounter in his at- 

 tempts. It was only after a laborious investigation of 20 years 

 that he was able to overcome them. 



His principal idea was to measure the quantity of water which 

 passes from one fixed degree of temperature to another equally 

 fixed by the combustion of a measured quantity of each sub- 

 stance. The apparatus whicfh he has contrived for this purpose 

 consists in a prismatic and horizontal receiver of copper, in 

 which there are two holes : one near one of the ends, to receive 

 a thermometer ; the other in the middle of the upper surface, 

 through which water is poured in, and Vv'hich is^ stopped by a 

 cork. Within this receiver there is a kind of fiat worm, which 

 covers the whole bottom without touching it, and which is 

 destined to receive the aerial products of combustion by means 

 of a vertical funnel soldered to its orifice. This worm returns 

 three times on itself, and its other extremity traverses horizon- 

 tally the upper surface of the receiver, to which it is contiguous. 

 The goodness of the whole apparatus depends upon the flat form 

 of the worm, which ought to transmit t'o the liquid contained in 

 the receiver all the portion of heat which it receives from the 

 substance that is burnt. 



But the receiver, when once hotter than the surrounding air,' 

 must lose a portion of the heat which it has received; and the 

 azote of the air which has served for the combustion, being with 



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