The Evolution of the Sciences 



The /3-rays form the trajectory of projectiles 

 eight thousand times lighter than the preceding 

 ones charged with negative electricity, and shot 

 off at a tremendous speed, between one hundred 

 and three hundred thousand kilometres per 

 second, these projectiles being called corpuscles or 

 electrons. Finally the 7 rays, analogous to the 

 X rays, are constituted beyond doubt in the 

 same manner as the X-rays, by perturbations of 

 the ether without any transference of material 

 masses or electric charges. 



But these are not the only things that are 

 emitted by radio-active bodies ; in the vicinity of 

 a specimen of radium bodies of all descriptions, 

 iron, indiarubber, wood, become active, that is to 

 say, emit all the rays we have described; but 

 their radio-activity, instead of being permanent, 

 decreases little by little until it becomes im- 

 perceptible in the course of a few minutes or days 

 as the case may be. The discoverers of this 

 phenomenon, M. and Mme. Curie, named it 

 induced radio-activity. This new form of energy, 

 produced by radium, is not radiated out like the 

 preceding ones ; it appears rather to diffuse like a 

 gas, emanating from the radium and spreading 



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