THE WORLD BEYOND OUR SENSES 



that is, about one-half as long as the red. It 

 is not possible as yet to go very far into the ultra- 

 violet; when it is we shall get very close to the 

 ultimate structure of matter. But even now it is 

 possible to detect invisible rays that have only a 

 quarter the length of the shortest visible ray 

 that is, about 100 /iju. 



Far out in the spaces beyond this beyond-the- 

 violet, in regions yet unexplored, lie probably the 

 Rontgen rays and yet others of which experiment 

 may disclose the effect even though it may not as 

 yet apprehend them directly. Far beyond the con- 

 fines of what we call matter, there seem to be mi- 

 nute particles, the tiny grains of which the relatively 

 huge atoms of matter are made. These particles 

 are thrown off from all highly heated or highly 

 electrified bodies, such as the sun, the electric light, 

 etc. They are the absurdly misnamed cathode 

 " rays " which Sir William Crookes, and latterly Pro- 

 fessor J. J. Thomson, of Cambridge, in England, 

 have studied so deeply. These, bombarding space 

 and all it holds with terrific speed (fifty to a hun- 

 dred thousand miles per second), give rise to all 

 sorts of perturbations of the ether, and of these the 

 X-rays are one. The cathode rays are made to 

 impinge upon certain chemical substances, and 

 through this impact we have that peculiar fluo- 

 rescence which shows through solid things. No 



47 



