Intelligence and Miscellaneous Articles, 151 



the other. New terms are thus introduced into m x and m 2 . 

 They are such as to seriously affect the values of these quan- 

 tities when x is small ; but they rapidly diminish by increase 

 of OS. 



If the new term in u be 



De-^^cos (4*m 2 £ — m#\/2 + E), 



the additional terms in m x are 



- Z+fL De-""^ 2 sin X- 4 T ~ ^ mxV2 cos X. 

 4m 2s/2-lm 



Those in m 2 are formed from these by making the first term 

 positive, and interchanging the sine and cosine of 



X=m#( N /2 + l)-E. 



o 



It appears from this investigation that Angstrom's method, 

 when applied with proper precautions, is theoretically capable 

 of giving very good results. But it is probable that, in prac- 

 tice, the thermometers will have to be supplanted by thermo- 

 electric junctions and a good dead-beat galvanometer. The 

 best thermometers, when employed for rapidly varying tem- 

 peratures, work by sudden starts. 



XVII. Intelligence and Miscellaneous Articles. 



ON THE PRINCIPLE OF THE CONSERVATION OF ELECTRICITY. 



BY M. G. LIPPMANN*. 



T 



[Second Paper, continued from vol. xi. p. 475.] 

 HE principle of the Conservation of Electricity is expressed (see 

 former article, Phil. Mag. vol. xi. p. 474) by the condition of 

 integrability 



aP_3Q ., a x 



a^-a^ - (a) 



Put thus in the form of an equation, the principle is capable of new 

 applications. It provides the means not only of analyzing certain 

 phenomena, but also of deducing from them the existence and the 

 law of new phenomena which experience has not yet made known 

 to us. I propose to give some examples of its applications. 



As a first example, I take the phenomenon discovered by M. 

 Boltzmann in 1875. This physicist proposed to measure the quan- 

 tity termed the dielectric power of gases. Por this purpose he 

 attaches to a firm stand, under the receiver of an air-pump, two 

 parallel metal plates, A, T, which form the two armatures of an 

 air-condenser. A is insulated ; T is connected to earth. The con- 

 denser is charged to a certain degree by placing plate A in commu- 

 nication for an instant with the pole of a battery whose other pole 

 * Translated from the Comptes Rendus, May 10, 1881. 



