Manchestef Memoirs, Vol. Iv. (1910), No. 3. 7 



to consider carefully the relations between the two men 

 and the circumstances under which Thomson's narrative 

 arose. 



Thomson, unlike the Henrys, was not a personal 

 friend of Dalton. He had made an adverse criticism of a 

 certain theory of which Dalton was the author, and the 

 author had made a stiff rejoinder/"' He thereupon paid 

 a visit to Manchester with the object of arriving at a full 

 understanding of the matter in question. The date of 

 the interview was August 27th, 1804, ^"d it was then, b\- 

 a fortunate accident, that Thomson learnt of the chemical 

 atomic theory of Dalton. 



Again, it is certain that Thomson and Dalton were 

 not subsequently in frequent communication with one 

 another on the subject. The sketch of the theory, which 

 Thomson published in 1807, was accompanied by the 

 note : — " In justice to Mr. Dalton, 1 must warn the reader 

 not to decide upon the notions of that philosopher from 

 the sketch which I have given, derived from a few minutes 

 conversation, and from a short written memorandum. 

 The mistakes, if any occur, are to be laid to my account, 

 and not to his ; as it is extremely probable that 1 may 

 have misconceived his meaning in some points."'' 



Nevertheless, this footnote errs on the side of caution. 

 Thomson's sketch of the theory, giving the first account 

 of it ever printed, was based on notes of what Dalton told 

 him, made during the interview, and only one phrase in it 

 is open to objection. He showed both zeal and care in 

 the matter, for it strongly interested him. 



In the "History of Chemistry," published in 1831, 

 Thomson says : — " I wrote down at the time the opinions 

 which he offered, and the following account is taken 



' '^ See Nicholson' s Joitni., vol. 8, p. 145, 1804 ; and Annals of Philo- 

 sophy, vol. 4, p. 65, 1814. 



^^ Thomas Thomson, "System of Chemistry," 3rd Ed., vol. 3, p. 425, 

 1807. 



