THE SEARCH FOR PRIMAL MATTER 



of vacuum in the tube, the little particles which 

 constitute the rays go whirling through space at 

 a tremendous rate. The slow ones flash by at 

 about a thousand miles a second. A rifle bullet, 

 for example, goes only a few thousand feet a second. 

 The swifter rays attain a velocity of above fifty 

 thousand miles a second, while latterly it has been 

 found that some other rays of an almost identical 

 character those discovered by Professor Becquerel, 

 and others by Madame Curie, in Paris reach half 

 the speed of light itself. The velocity of light is 

 about one hundred and eighty-four thousand miles 

 per second. Even a slow imagination leaps in- 

 stantly to the thought that yet other travellers 

 will be found which go as fast as light ay, which 

 are light itself. 



Knowing the velocity, and knowing the constant 

 relation between a given mass of the cathode rays 

 and the charge of electricity they transport from 

 one end of the tube to the other, would it now 

 be possible to measure the mass and charge of 

 each individual particle? It was a daring thought. 

 But here, as so often happens, a curious discovery 

 in quite another field came to Professor Thomson's 

 aid. 



In the laboratory at Cambridge, Mr. R. T. C. 



Wilson had been working on some odd perform - 



of the R< nitLrt'n rays. He took a chamber, or 



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