Mancliester Memoirs, Vol. Iv. {igio), No. 4. ii 



abandon it — in 1785, he says — and was absolutely the 

 first to write against it in the English language. His 

 " Comparative View of the Phlogistic and Anti-phlogistic 

 Hypotheses" (1789) is primarily a refutation of the 

 phlogiston theor}'. Incidentally, it shows that he had 

 been carrying on experimental work of his own, and 

 also that he had improved on his uncle's speculations. 

 Out of atoms and molecules he fashioned a theory of 

 chemical combination and chemical dynamics as well, so 

 that his book is remarkable as containing the first 

 attempt at a comprehensive system of chemistry, based 

 on the atomic theory. 



William Higgins regarded the atom of a gas as a 

 hard particle surrounded by an "atmosphere of fire.""" 

 He believed firmly that chemical combination occurs in 

 definite proportions, and supposed that it occurs, in the 

 first place, atom with atom. He regarded the molecule 

 of water as formed by the linking of one atom of hydrogen 

 with one of oxygen. " Water is composed of molicules 

 formed by the union of a single ultimate particle of 

 dephlogisticated air to an ultimate particle of light inflam- 

 mable air . . . they are incapable of uniting to a 

 third particle of either of their constituent particles."^ 

 In short the formula OH expresses his conception of the 

 molecule of water. 



William Higgins was better acquainted with the facts 

 of chemical composition than his uncle, for he did not 

 believe in phlogiston, and he recognised oxygen as one of 

 the elements. He was aware of a number of cases in 

 which elements combine in more than one proportion, 

 and in such cases continued to apply the atomic theory. 



** " Comparative View of the Phlogistic and Antiphlogistic Hypotheses," 

 pp. 14, 37, 81, 133. 



Ibid., p. 37. 



