1813.] 



Imperial Institute of Francs, 



38^ 



the ^condensation of the vapour of water and alcohol, obliges us 

 to notice ocly the general results. He determine?^ for example, 

 that the temperature of water at the moment of its formation by 

 the combination of oxygen and hydrogen is eight times higher 

 than that of iron heated so as to appear red in broad day-light ; 

 and that boiling water, in passing to the state of vapour^ renders 

 latent 1040 degrees of heat, or, which comes to the same thing, 

 that this quantity is evolved when the vapour of water is con- 

 densed. 



According to the same experiments, the capacity of the vapour 

 of water for heat diminishes with its temperature^ and from the 

 phenomena relative to the vapour of alcohol, we may conclude 

 that the oxygen and hydrogen which enters into the compositiou 

 of this liquid are not in the state of water. 



The Class had proposed, as one of its physical prizes, the 

 determination of tlie capacity of oxygen gas, carbonic acid gas, 

 and hydrogen gas, for heat. This prize lias been voted to a 

 memoir of M. M. Francois Deiaroche and Berard. These two 

 philosophers have not satisfied themselves with the cases pro- 

 posed ; they have taken a general vievv^ of the matter, and deter- 

 mined the specific heat of other gases; and that of air and 

 vapour under different pressures. Among other interesting 

 particulars, they have found that the capacity of a given mass 

 of air increases with its bulk. Reducing all the capacities to 

 that of water, they have drawn up the following table of their 



labours : — 



Capacity of Water l-OOOO 



Atmospheric air 0-266D 



Hydrogen gas. 3*2936 



Carbonic acid gas , . .0-2210 



Oxygen gas 0*2361 



Azotic gas 0°27r>4 



Nitrous oxide gas 0*28G9 



Olefiant gas 0°4207 



Carbonic oxide gas 0*2884 



Aqueous vapour 0*8470 



Heat penetrates all bodies.,^ It contributes essentially to their 

 dilatation, and it is squeezed out, to use the expression, when- 

 ever they are reduced, by any operation whatever, to smaller 

 dimensions. Thus we know, by experiments made ten years 

 ago at Lyons by M. Mollet, that air suddenly compressed gives 

 out heat, and that this heat is accompanied with light Th^^ 

 phenomenon has given origin to the convenient instrument by 

 v/hich tinder is kindled by the pressure of a piston. 



M. Dessaignes, an ingenious philosopher of Ve»dome^ ia 



6 



