342 Mr. C. Akin on a New Method for the Direct Determination 



are contested, others, such as that of Clement and Desormes, 

 proceed upon principles of which it is more than doubtful 

 whether they have been formed with a sufficient regard to all 

 the circumstances inherent in the case, the importance of 

 several among the latter having only become felt since the 

 resuscitation of the Baconian or Hermannian theory of heat*. 

 Whilst such is the case with regard to the more circuitous 

 methods, other methods, in which it was intended to deduce the 

 numerical values of the specific heats of gases under constant 

 volume from experiments more nearly corresponding in their 

 circumstances to the definition of the magnitudes they were de- 

 signed to furnish, have failed to yield results possessing the con- 

 fidence of philosophersf. Under these circumstances, and for 

 the reasons above stated, it seems important that some new 

 method should be devised, direct in theory and trustworthy in 

 practice, capable of supplying the want of knowledge of the 

 exact and real specific heats of gases in a manner which might 

 command approbation. The real merits of any such method, of 

 course, could only be tested by actual experience ; but, although 

 the method to be described in this paper, on the contrary, is 

 only a scheme untried by experiment, it is yet hoped that its 

 publication will not be without utility. For even if the plan, as 

 a whole, should fail in practice in the case for which it has been 

 more especially devised, it will yet be found to possess some new 

 features, capable of wide and useful application elsewhere. 



] . In order to clearness, we shall begin by illustrating the prin- 

 ciple of the method here suggested, by the aid of a simply sup- 

 posititious case. Let, then, a quantity of gas be supposed to be 

 enclosed in a thin globular shell of a substance considered as 

 impervious to, though a non-absorbent of heat. Let this sub- 

 stance, or the shell which is supposed to be made of it, further 

 be assumed to be inextensible by pressure, though liable to dis- 

 ruption when opposed by a certain pressure whose magnitude 

 shall be supposed to be known. Finally, let the terminals of a 

 galvanic battery be taken to perforate the above shell in a man- 

 ner not allowing of conduction by means of the shell (nor, of 

 course, the efflux of the gas), but permitting of the passage of 

 the electric current, derived from the battery, in a large platinum 

 spiral suspended within the shell. If the battery be set in action, 

 after a certain interval of time the temperature of the gas con- 

 tained within the shell, we assume, shall become sufficiently great 



* As is well known, Bacon first defined heat as molecular motion ; but 

 it was Hermann, in his Phoronoraia (p. 376), who first defined heat as mo- 

 lecular energy or vis viva. 



t See, e. g., M. Regnault's remarks in the second volume of his Rela- 

 tion, &c. 



