THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE, 



[FIFTH SERIES.] 

 MARCH 1897. ^^^#7 C 



XXVI. T/*e Genesis of Dalton s Atomic Theory. 

 By H. E. Roscoe an<# Arthuk Haeden *. 



THE criticism by Debus (Phil. Mag. 1896, xlii. p. 350) of the 

 opinions expressed in our ( New View of the Origin of 

 Dalton's Atomic Theory } demands some notice at our hands. 

 The problem of the origin of the atomic theory is one not 

 only of importance but of some complexity, dealing as it does 

 with the gradual progress of thought in the author's mind, 

 and depending for its solution to a great extent on indirect 

 and fragmentary evidence. 



Jn the first place Debus regards the whole question from 

 a point of view which differs from ours. After showing that 

 Dalton in his earliest papers applied the idea of atoms to ex- 

 plain the physical properties of gases, Debus adds (p. 352) : — 

 " In 1803 he discovered a method how to determine the rela- 

 tive weight of atoms, and added to the atomic philosophy a 

 series of principles. The group of principles so added by 

 Dalton I propose to call ' Dalton^s Atomic Theory/ " By 

 "group of principles," Debus means Dalton's well-known 

 rules of chemical synthesis (N. S. p. 211). 



We, on the other hand (R. and H. p. 51), have clearly 

 stated that we consider the essential feature of Dalton's 

 atomic theory to be "the idea that chemical combination 

 takes place between particles of different weights," and it is 

 the genesis of this idea, and not merely the origin of the 



* Communicated by the Authors. 

 Phil Mag. S. 5. Vol. 43. No. 262. March 1897. 



