MancJiester Memoirs, Vol. Iv. (1910), No. 3. 11 



with the appearance of a deliberate, strategical, irresistible 

 advance. On examination his narrative, in spite of its 

 grand air, is found to throw much less light than it pro- 

 mises on the line of thought and train of investigation 

 which he pursued. It is excessively abstract in tone, and 

 avoids going into details and particulars and instances. 

 It does not tell us what we want to know most, how and 

 when Dalton arrived at the law of multiple proportions, 

 and the part played by the law in the construction of the 

 theory. Information on these matters is what is wanted, 

 and anything else is beside the point. 



Yet there is one novel element in Dalton's account. 

 This is the suggestion that the formation of the chemical 

 atomic theory took place subsequently to the amendment 

 of the diffusion theory. But, as the notebooks show, the 

 chemical theory was formed in 1803. Hence, Roscoe and 

 Harden conclude that iSo5,the date which Dalton assigns 

 to his amended diffusion theory, should be 1803.^ 

 Reasons will be given later, in a paper on Dalton's 

 physical atomic theory, for thinking that the narrative 

 is doubtful on the only point on which it presents any 

 novelty. 



Conclusion. 



There are in existence yet other accounts of this 

 matter. One is given by Dalton's pupil, Joseph A. Ran- 

 some,^* and another by Dalton himself. This was in the 

 lecture which he delivered to the members of the 

 Mechanics' Institute in Manchester on October 19th, 

 1835.''^ The main feature, which ^/Z the accounts have in 



- => op. tit., p. 25. 



-* W. C. Henry, Op. dt., pp. 220-222. 



-* Manchester Times, October 25, 1835. 



