144 PHYSICAL SCIENCE 



m being expressed in grams, and e in electro- 

 magnetic units of electricity. 



Thus, within the limits of experimental error, 

 the values of m/e are independent of the nature 

 of the residual gas left in the vacuum tube. 

 Moreover, in these experiments, and in a further 

 series due to H. A. Wilson, the results were 

 shown to be the same whatever metal was used 

 to form the cathode. In all circumstances the 

 mean velocity is very high, being about one- 

 twelfth that of light, and the mean value of m/e 

 is 1.3 X io~^ which makes the reciprocal ratio 

 e/m about 7.7 x lO^ 



Since the date of Thomson's original in- 

 vestigation, these measurements have often been 

 repeated. More recent results, especially those 

 of Millikan, give values for 7;i/e of 5.64 x io~^ and 

 for e//u of 1.77 X lo"^. 



Now in liquid electrolytes, the passage of 

 one electro-magnetic unit of electricity evolves 

 io~^ gram of hydrogen. Thus, in this case, the 

 ratio vi/e is about IO~^ or about eighteen hundred 

 times more than 5.64 xio~^ its value for the 

 negative particle in a cathode ray. 



But, as we have already seen (p. 134), by an 

 application of C. T. R. Wilson's beautiful experi- 

 ments on the electric formation of clouds, Thomson 

 has proved that the individual charge on all the 

 gaseous ions examined is the same as the charge 

 on the ions in liquid electrolysis, and this result 

 has been confirmed by other methods. Although 



