MECHANICS AND RADIUM. 207 



ceptions. What had been proved only in the case 

 of the cathode corpuscles has been extended to all 

 bodies. What we call mass would seem to be nothing 

 but an appearance, and all inertia to be of electro- 

 magnetic origin. But if this be true, mass is no 

 longer constant; it increases with the velocity: while 

 apparently constant for velocities up to as much as 

 600 miles a second, it grows thenceforward and be- 

 comes infinite for the velocity of light. Transversal 

 mass is no longer equal to longitudinal mass, but only 

 about equal if the velocity is not too great. Principle 

 B of mechanics is no longer true. 



III. 



Canal-Rays. 



At the point we have reached, this conclusion may 

 seem premature. Can we apply to the whole of 

 matter what has only been established for these 

 very light corpuscles which are only an emanation 

 of matter and perhaps not true matter? But before 

 broaching this question, we must say a word about 

 another kind of rays — I mean the canal-rays, Gold- 

 stein's KanalstraJilen. Simultaneously with the cathode 

 rays charged with negative electricity, the cathode 

 emits canal-rays charged with positive electricity. In 

 general these canal-rays, not being repelled by the cath- 

 ode, remain confined in the immediate neighbourhood 

 of that cathode, where they form the "buff stratum'" 

 that is not very easy to detect. But if the cathode is 

 pierced with holes and blocks the tube almost com- 

 pletely, the canal-rays will be generated behind the 



