24 CLAU8IUS ON THB MECHANICAL EQUIVALENT 



riments, and hence we can write 



If this expression be compared with that found by Riess for 

 the heating (22), it is seen that to make both proportional it is 

 only necessary to assume that in the jars of both batteries, 

 although they were not equal, the quantities k and k' possess 

 nearly the same value ; and this assumption is peculiarly jus- 

 tified by the fact that Riess found by direct measurement, that 

 when they were combined the electricity distributed itself over 

 the batteries in proportion to their surfaces, and this, according 

 to (24), could only be the case when k was =A;'*. 



Riess altered his experiments so that he increased the length 

 of the connecting wire, and observed the consequent diminution 

 of heat at a certain place. The results of these observations 

 coincide in general with those already mentioned, and we will 

 therefore pass over them here, and also some other experiments 

 described in the same paper. 



In regard to the cascade battery, we possess experiments from 

 Dovef and Riess J. It consists, as is known, of a number of 

 single jars or complete batteries, insulated and so connected with 

 each other, that the exterior coating of the first is connected 

 with the interior coating of the second, the exterior of the second 

 with the interior of the third, and so forth. Only the inner 



♦ As the quantities k and k', according to the above, depend principally upon 

 the thickness of the glass of both batteries, it appeared to me of interest to 

 ascertain these thicknesses ; while this Memoir was still in the press, 1 therefore 

 requested M. Riess to make the measurement, and am indebted to his kindness 

 for the following communication. In the small jars (those of the second bat- 

 tery) the thickness of the glass varies considerably, its mean thickness being 

 1^ Paris line. The large jars (those of the first battery) he was unable him- 

 self to measure as they were closed above, and he has therefore measured two 

 othorg which he had made at the same time with the former, and with the in- 

 tention of being used along with them. The glass in these is nearly imiform 

 and 14 line thick. As an absolute equality of the glass thicknesses was not to be 

 expected under the circumstances, and as it is not a necessary consequence of 

 the assumed equality of k and W, inasmuch as the latter are also to a certain, 

 although subordinate extent, dependent on the shape and magnitude of the" 

 jars which are different in both batteries, I believe that the coincidence of the 

 numbers 1^ and 1^ is sufficiently exact. 



f Pogg. Ann. vol. Ixxii. p. 406. \ Pogg. Ann, vol. Ixxx. p. 349. 



