191 1.] WILSON— COXSTITUTIOX OF THE ATOM. 373 



this were ?o the calculation of /3 given above would not be affected 

 as can be easily seen. 



The equation ( 477 '3/? )3 =.-J„j-i — A,„_^i gives 



^„=(^>+(„,-,)(^;yy. 



This equation enables the atomic weights of a series of similar 

 elements to be approximately calculated if that of the first in the 

 series is known. For example, if we take Aj^=i we obtain the 

 following numbers : 



m Am 



1 I H=i 



2 6 L\ = y 



3 18 Na = 23 



4 40 K = 39 



5 77 Rb = 85 



6 129 Cs=i33 



If we take A^ = c) we obtain the following numbers: 

 /;/ Am 



1 9 Be = 9 



2 24 Mg^24 



3 51 Ca = 40 



4 92 Sr = 87 



5 150 Ba=i37 



6 230 Ra = 226 



It will be seen that the numbers given by the approximate 

 formula deduced from Sir J. J. Thomson's theory agree approxi- 

 mately with the atomic weights. I think this must be regarded as 

 strong evidence that there is a considerable element of truth in 

 the theory. 



I believe that this is the first time that a definite theory of 

 atomic structure has been worked out sufficiently to enable a com- 

 parison between theoretical results and the known atomic weights 

 to be made. 



McGiLL University, 

 Montreal. 



