2 Meldrum, Development of the Atomic Theory. 



I. The Itifliience of J. B. Richter. 



William Charles Henry held a conversation with 

 Dalton on the subject of the origin of the theory, in which 

 special importance was given to the influence of J. B. 

 Richter. " The speculations which gave birth to the 

 atomic theory were first suggested to Mr. Dalton by the 

 experiments of Richter on the neutral salts ... a 

 table was formed exhibiting the proportions of the acids 

 and the alkaline bases constituting neutral salts. It 

 immediately struck Mr. Dalton that if these saline com- 

 pounds were constituted of an atom of acid and one of 

 alkali, the tabular numbers would express the relative 

 weights of the ultimate atoms. These views were con- 

 firmed and extended by a new discovery of Proust,"' &c. 



This narrative received strong support from William 

 Henry (the father of W. C. Henry), who held more than 

 one conversation with Dalton on the subject. The 

 following is part of a minute, dated February 13, 1830, of 

 one of these conversations : — " Confirmed the account he 

 before gave me of the origin of his speculations leading to 

 the doctrine of simple multiples, and of the influence of 

 Richter's table in exciting these views."^ 



The Henrys, father and son, are entitled to the fullest 

 credence in this matter. Their acquaintance with Dalton 

 was more intimate than that of any other man of science, 

 Peter Clare excepted. W. C. Henry was in turn the 

 pupil, the friend and the biographer of Dalton. In the 

 preface to the Biography, he mentions with just pride 

 Dalton's " almost lifelong friendship with my father, 

 never shadowed by even a passing cloud " ; and he refers 

 also to " his early favourable notice of and unceasing 

 benevolent regard towards myself, thoughtfully mani- 



' W. C. Henry, "Memoirs of Dalton," p. 84. 

 - Ibid., p. 63. 



