204 SCIENCE AND METHOD. 



Mechanics, the inertia of a body opposes all variation 

 in its velocity. Self-induction is an actual inertia. 

 Everything takes place as if the current could not be 

 set up without setting the surrounding ether in motion, 

 and as if the inertia of this ether consequently tended 

 to keep the intensity of the current constant. The 

 inertia must be overcome to set up the current, and it 

 must be overcome again to make it cease. 



A cathode ray, which is a rain of projectiles charged 

 with negative electricity, can be likened to a current. 

 No doubt this current differs, at first sight at any rate, 

 from the ordinary conduction currents, where the 

 matter is motionless and the electricity circulates 

 through the matter. It is a convection current., where 

 the electricity is attached to a material vehicle and 

 carried by the movement of that vehicle. But Rowland 

 has proved that convection currents produce the same 

 magnetic effects as conduction currents. They must 

 also produce the same effects of induction. Firstly, if 

 it were not so, the principle of the conservation of 

 energy would be violated ; and secondly, Cremien and 

 Pender have employed a method in which these effects 

 of induction are directly demonstrated. 



If the velocity of a cathode corpuscle happens to 

 vary, the intensity of the corresponding current will 

 vary equally, and there will be developed effects of 

 self-induction which tend to oppo.se this variation. 

 These corpuscles must therefore possess a double 

 inertia, first their actual inertia, and then an apparent 

 inertia due to self-induction, which produces the same 

 effects. They will therefore have a total apparent 

 mass, composed of their real mass and of a fictitious 

 mass of electro-magnetic origin. Calculaticjn shows 



