14 Meldrum, Development of tlic Atomic Theory. 



must be set aside. No great penetration of mind is 

 required to divine "the fixed and uniform principle" 

 on which Higgins proceeded in assigning the atomic 

 composition of substances. Although he does not himself 

 mention Newton, there is no room for doubt that 

 Newton's conception of "particles mutually repulsive" 

 w^as the germ of the theory. Bryan Higgins, who was a 

 student of Newton, made use of this conception, and he 

 communicated it to his nephew. The indebtedness of the 

 nephew to the uncle is as plain as the indebtedness of 

 the uncle to Newton. 



There remains now for consideration a remark by 

 Roscoe and Schorlemmer, that "all upholders of an 

 atomic theory" previous to Dalton, "including even 

 [William] Higgins, had supposed that the relative 

 weights of the different elements are the same."-'^ 



This is a sweeping assertion, of which no proof has 

 ever been offered. One can hardly believe that Newton 

 expressed such an opinion, and it is certain that William 

 Higgins did not. Regarding the oxidation of tin, he 

 supposed that lOO grains of the metal may combine with 

 7|- or with 15 grains of oxygen.'""^ But since he held 

 the oxidation series of an element to be RO, RO,, RO., 

 etc., his figures for tin mean that the atom of the 

 metal was supposed to be much heavier than one 

 atom, or even two of oxygen. Possibly Roscoe and 

 Schorlemmer's statement is based on the case of oxygen 

 and sulphur, which Higgins held to have the same 

 atomic weight. But this conclusion of his depends 

 for one thing on the supposition that the molecule of 

 sulphurous acid (the substance SO2, not H.SOg) is com- 

 posed of one atom of each element, and for another on 



-" Koscoe and Schorlemmer, " Non-Metallic Elements," p. 35, 1905. 

 "■"* "Comparative View,'" p. 275. 



