NEW CONCEPTIONS IN SCIENCE 



charge beyond all doubt, he was able to go further, 

 and by means of an ordinary electroscope actually 

 measure the amount of this charge. 



Here, at last, was solid ground. Professor Thom- 

 son was able to measure so accurately the charge 

 that he could prove that a certain space shot 

 through with cathode rays always contained a 

 definite amount of electricity. In other words, 

 he could measure the relationship or ratio between 

 a given mass or bulk of matter, as he conceived 

 the cathode rays indubitably to be, and the charge 

 they bore. This he expressed in his mathematical 

 way by saying that the ratio (^- e ) was known. 



It will be remembered that Professor Crookes 

 had observed that the cathode rays were bent in 

 any desired direction by means of a magnet. But 

 that the same bending would take place when an 

 outside charge of electricity was brought up to the 

 rays long eluded demonstration. This latter Pro- 

 fessor Thomson succeeded in bringing out clearly 

 by another of the clever experiments with which 

 the whole history of this investigation has been 

 filled. 



By means of parallel plates bearing an electro- 

 static charge, Professor Thomson proved that elec- 

 tricity could bend the rays equally with a magnet. 

 And this enabled him to measure the speed of the 

 "rays." He found that, varying with the degree 



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