Manchester Memoirs, Vol. Iv. {\gio), No. 4. 13 



decide on the necessity of fixed composition as a result. 

 But we obtain no results affecting chemical philosophy "'^ 

 In this paper I have shown that Bryan Higgins' theory, 

 far from being " ancient," is a development of Newton's, 

 and that instead of his theory being obscure, and leading 

 to confused ideas regarding chemical composition, it led 

 to a view of the doctrine of fixed proportion, of which the 

 fault was that it was too narrow and rigid. 



This difference of opinion, great and hopeless as it 

 may seem, admits of the simplest explanation. Smith's 

 estimate is based upon the" Syllabus" of the year 1775, and 

 upon certain incidental remarks on atoms which he found 

 in the book on "Acetous acid." He was not acquainted 

 with the "Philo-sophical Essay on Light," which assuredly 

 is not the place where one should expect to find the 

 chemical speculations and ideas regarding atoms, of which 

 nevertheless it is full. Had Angus Smith read this book 

 he must have i)erceived the clue to the Higgins' ideas, 

 namely, the connection with Isaac Newton. He must 

 then have seen that Bryan Higgins was the first to 

 explain the constant chemical composition of salts in 

 terms of atoms, and that his theory was only too definite 

 and rigid, for it led him to maintain that an acid and an 

 alkali could combine in only one proportion, namely, 

 atom with atom. 



W. C. Henry, in his estimate of William Higgins, 

 shows the fatal weakness of failing to see the basis of the 

 theory. Having given Higgins' views regarding the 

 atomic composition of the oxides of nitrogen, he remarks : 

 " It is evident that Mr. Higgins was guided by no fixed 

 and uniform principle, in assigning the atomic constitution 

 of the above compound bodies."-'^' This verdict also 

 •-» Ibid., p. 173. 



'-'• W. C. Henry, " Memoirs of Daltoii," p. 77. 



