OP AUTS AND SCIENCES. 



121 



I ■ 

 _ J — >■ 



i 



Fig. 7. 



It is perhaps unnecessary to call attention to the fact that the ca- 

 pacity of a dielectric for rapid discharges is very different from its 

 capacity for slow discharges. In the paper of Lorenz, already cited, 

 the value of the dielectric capacity of glass was determined by slow 

 methods, and used to test an equation in which the capacity of glass 

 appears under very rapid charging and discharging. 



Boltzman * and Klemencin f have experimented on the specific in- 

 ductive capacity of gases and vapors, and it is seen from their results 

 that the agreement between the square root of the capacities of the 

 simple gases and ix, the index of refraction for light of these gases, is 

 quite close, as is demanded by Maxwell's electromagnetic theory of 

 light. A marked difference, however, was found to exist in the case 

 of more complicated molecules, — sulphurous acid, or ethyl bromide, for 

 instance. It is probable that the changes of specific capacity of hete- 

 rogeneous media under rapidly alternating forces constitute an impor- 

 tant factor in considering the possible agreement between Maxwell's 

 theory of light and the results of experiment. 



In order to see if an intense magnetic field could modify the trans- 



* Pogg. Ann., Vol. CLI. p. 403, 1875. 



t Abstract of Journal of the Society of Telegraphic Engineers, 1886, p. 108. 



