]\TancJiestey Memoirs , Vol. /:-. (1910), No. 3. 



III. The Development of the Atomic Theory : (2) The 

 various Accounts of the Origin of Dalton's 

 Theory. 



By x^NDREW NOKMAN MELDRUM, D.Sc. 



(Carnegie Kcsearrh Felloiv). 



(Communicakd by Professoi- H. B. Dixo/i, M.A., F.R.S.) 

 Received June, igio. A'cad Novetnher ist, igio. 



The origin of Dalton's theory remains one of the 

 outstanding problems in the history of chemistry. Yet 

 the amount of material at hand for the study of the 

 subject is considerable. Dalton's note-books, discovered 

 within the last twenty years in the rooms of the Man- 

 chester Literary and Philosophical Society, contain 

 material of the highest value for the purpose. Also, 

 there are on record important accounts of the genesis of 

 the theory by three different persons. One is given by 

 William Charles Henry, another by Thomas Thomson, 

 and another by Dalton himself Although there are yet 

 other accounts in existence, these three are the only ones 

 that need be considered in detail here. 



One of the principal results of this paper is to show 

 that these various narratives came, originally, from 

 Dalton himself. In the nature of the case, this is what 

 was to be expected. At the same time the discrepancies 

 between these accounts have to be explained. In the 

 course of the paper it will become more and more 

 evident that the person responsible for them is Dalton. 



December lyth, igio. 



