On the Mode of the Propagation of Sound. 441 



The same experiment was then repeated, with only this differ- 

 ence, that a voltameter was enclosed in the seventh muffle. 

 In this the quantity of heat k — a was obtained, where a (as 

 shall presently be shown) denotes the quantity of heat which 

 was consumed in the chemical decomposition of the electro- 

 lyte in the voltameter. In this way Favre found, as the equi- 

 valent for the chemical decomposition of water, 34204, and 

 for the decomposition of sulphate of copper 26568 thermal 

 units. 



Thereupon the following experiments were made : — The 

 voltameter was taken out of the calorimeter No. 1, and placed 

 in another calorimeter, No. 2 ; while the series and rheostat 

 remained in No. 1. It was now found that calorimeter No. 1 

 indicated, on the electrolysis of water, 54235 heat-units less 

 than in the first experiment — that is, when the series and rheo- 

 stat were enclosed in No. 1 and no voltameter was inserted in 

 the circuit. When the voltameter contained the copper- 

 solution, 38530 units of heat less than in the first experiment 

 were obtained in the same calorimeter. The calorimeter 

 No. 2 gave, in the former case, a heating of 20335, and, in 

 the latter, one of 12445 units. 



Upon this Favre asks, What can be the reason that the 

 large quantity of heat that has disappeared in the series is 

 again found in the calorimeter No. 2 ? This cause, he con- 

 tinues, cannot be referred to the physical resistance of the vol- 

 tameter ; for this is so insignificant that it might almost be 

 neglected in comparison with the resistance of the rheostat. 

 According to his view the cause is to be sought in the cir- 

 cumstance that the substances which take part in the chemical 

 processes (oxygen, hydrogen, &c.) are found now in statu 

 nascenti, now in the ordinary state. This explanation appears 

 to me quite unsatisfactory. Even if it be assumed that such 

 secondary chemical processes take place in the voltameter, 

 they can certainly cause a heating of the voltameter, but they 

 cannot possibly account for the great loss of heat which takes 

 place in the series and rheostat. 



[To be continued.] 



LIX. Mode of the Propagation of Sound, and the Physical Con- 

 dition determining its Velocity on the Basis of the Kinetic 

 Theory of Gases. By S. Tolver Preston*. 



1. O INGE the kinetic theory of gases is now generally ac- 

 *P cepted by physicists, affording, as it does, a rational 

 explanation of the physical qualities and deportment of gases 

 * Communicated by Professor Clerk Maxwell, 



