144 VARIABLE MASS [CH. xiv. 



agrees with observation, in absolute numerical value, 

 any better than Thomson's formula does ; nor do I 

 obtain even from Thomson's formula exactly the 

 numbers that he quotes in his American lectures ; 

 but to go into the whole matter would be inappro- 

 priate here, nor is it necessary, since the theoretical 

 differences only concern details that could doubtless 

 be removed by a little discussion : it will only become 

 necessary to go into them more fully when the 

 difficulties of the experimental observation are still 

 further overcome, and when even more accurate and 

 trustworthy results are obtained. * 



I have taken the table of Kaufmann's best results, 

 as published in the Physikalische Zeitschrift 4, 

 1902-3, p. 55, and calculated them out by aid of 

 the expression given above on p. 133. 



The results are tabulated below. I quote his given 

 experimental values for x and y, together with the 

 values he gives for /3, or u/v, or what I have called 

 sin 0; and then after reckoning out <(#), which repre- 

 sents the theoretical ratio m/m according to Thomson's 

 theory, I have put a column of y/x 2 ; which should 

 correspond, at least proportionally, to the same 

 quantity as experimentally determined ; and I like- 

 wise quote a column of f^(/#), which represents the 

 same quantity calculated according to Abraham's 

 formula (p. 143). (The numerical agreement of y/x 2 

 with a mean mass ratio, without any constant factor 

 other than unity, must be accidental.) 



*The results of Kaufmann's subsequent work will be discussed in 

 Appendix M. 



