Law of Atomic Weights. 505 



add strength to the evidence that the physical properties of 

 the elements are the result of general laws, the truth of which 

 proposition is the basis of the present forecast, and was the 

 conclusion to which the original investigation led. 



What that investigation claims to have established may be 

 put briefly. Evidence that seemed conclusive was adduced 

 that the atomic weights of the elements of even and of odd 

 atomicity conform to two slightly divergent laws, the cause 

 of which is obscure, and which, therefore, we can only grope 

 for empirically. 



They both, if fully worked out, would furnish values that 

 lie close to the positions fixed by a simpler law, which is 

 either the logarithmic law plotted down upon Plate IV. of 

 last month's Phil. Mag., or the law represented by some 

 other curve which throughout a considerable extent — from 

 lithium to uranium — keeps close to that logarithmic curve. 



Of such curves it is mathematically known that the number 

 is unlimited. All but a few of these wall represent laws that 

 are so improbable that they may at once be rejected. This, 

 however, may be the most we can do : between the few curves 

 that remain we have not the data for discriminating with 

 certainty so long as we can only investigate the laws of 

 atomic weights empirically. 



Under these circumstances, what we seem justified in 

 regarding as established is, that there exist two definite laws 

 which control the atomic weights of the elements of even and of 

 odd atomicity ; and that these laws are adequately represented 

 hy the law presented by some one of the above family of curves 

 supplemented by one set of regulated small deviations for 

 the artiads and another set for the perissads : with all the 

 consequences of this suggestive fact. The law T s of the 

 deviations were less satisfactorily worked out ; enough, how- 

 ever, to show the marked difference between them, and some 

 of their main features, including a predominance in both of 

 a period of 18 places of the Mendeleeff series. 



Persons making use of the diagram in last month's Phil. 

 Mag. are requested to insert upon it the following approxi- 

 mate atomic -weights. 





Xeon 



. . . 20 





Helium . 



. . 4 



Krypton . 



. . 81 



Argon . 



. . 396 



Xenon . . 



. . 127 



I remain, Gentlemen, 

 30 Ledbury Road. W. Faithfully yours, 



September 1902. G. JOHNSTONE STONEY. 



Phil. Mag. S. 6. Vol. 4. No. 9.2, Oct. 1902. 2 L 



