PROPERTIES OF CORPUSCLES. 69 



It was soon discovered that the phosphorescence in the 

 end of the bulb was caused by something coming from the 

 neighborhood of the cathode, for a solid placed between 

 the cathode and the end of the bulb casts a shadow on the 

 bulb. An example of this effect is shown in Fig. 15, where 

 the shadow is caused by a maltese cross of mica, placed 

 between the cathode and the end of the bulb. The shape 

 of the shadow shows that the cause of the phosphorescence 

 travels in straight lines, and that, moreover, it comes 

 straight from the cathode. It is to the agent producing 

 this phosphorescence in the bulb that the name, cathode 

 rays, has been given. 



Fig. 16. Photographic representation of a vacuum tube in action. 



Now, cathode rays constitute simply a beam of corpuscles ; 

 that is, they consist of negatively electrified particles hav- 

 ing a velocity equal to that of corpuscles obtained in other 

 ways, and their mass is a thousand times less than the mass 

 of a hydrogen atom. 



PHOSPHORESCENCE . 



A very large number of bodies give out a phosphorescent 



