Manchester Memoirs, Vol. Iv. (191 1), No. 19. 3 



Thomas Thomson, John Murray, T. C. Hope, John Gough, 

 Humphry Davy, and Claude Louis Berthollet. 



Dalton's chemical theory was formed by the 6th 

 September, 1803,'^ ^"^ he proceeded forthwith to extend 

 and apply it, and make it known in every direction. His 

 first efforts, naturally, were made at this Society, where, 

 on the 7th October, he read a paper in which the theory 

 was employed in order to explain the absorption of a gas 

 by water. What he endeavoured to do was to establish 

 a connection between the solubility of a gas and its atomic 

 weight. This paper, as published in 1805, comes to an 

 end with a table of atomic weights, of various simple and 

 compound substances, remarkable as the earliest of the 

 kind ever printed. There is no reason to doubt that the 

 paper contained a table of atomic weights when it was 

 read, but Dalton certainly extended the table before going 

 to press. 



Dalton was eager both to have his ideas put into 

 circulation and to have a resume of them put on record. In 

 London, in the winter of 1803- 1804, he gave a course of 

 lectures at the Royal Institution, i« which he included a 

 brief outline of the theory. He left this for publication 

 in the Journals of the Institution, but, as he ironically 

 remarked afterwards, " he \yas not informed whether that 

 was done."' Humphry Davy was at the Institution at 

 the time, but Dalton did not succeed in arousing in him 



- A paper of his, read before this .Society on November 12th, 1802, 

 contains a reference to the chemical theory. This is the paper "on the 

 propoition of the several gases, or elastic fluids, constituting the atmosphere." 

 But it was not published till 1S05, and Koscoe and Harden think it was re- 

 written in the meantime, for it includes results, on the combination of nitric 

 oxide and oxygen, which Dalton did not obtain till 4th August, 1803. 

 (Roscoeand Harden, " New View of the Origin of Dalton's Atomic Theory,' 

 p. 35). I cannot myself doubt that this conclusion is the correct one. 



•' "Xew System of Chemical Philosophy," 1808, Preface. 



