JOHN D ALTON 511 



predecessors — Xewton. Dalton encountered certain phenomena, such 

 as multiple and definite proportion, aqueous vapor as a distinct con- 

 stituent of air, and, seeking for the simplest common representation, 

 found it in Newton's well-known doctrine. For example, he says : 



According to this view of the subject [heat], every atom has an atmosphere 

 of heat around it, in the same manner as the earth or any other planet has its 

 atmosphere of air surrounding it, which can not certainly be said to be held by 

 chemical affinity, but by a species of attraction of a very different kind. 21 



And he quotes from Xewton : 



All bodies seem to be composed of hard particles. . . . Even the rays of 

 light seem to be hard bodies, and how such very hard particles which are only 

 laid together and touch only in a few points, can stick together, and that so 

 firmly as they do, without the assistance of something which causes them to be 

 attracted or pressed towards one another, is very difficult to conceive. 25 



This was the secret of the opposition of Hope and, later, of Faraday's 



complaint. In a letter, dated January 2, 1811, Hope wrote to Dalton 



as follows : 



I need not conceal from you that I am by no means a convert to your doc- 

 trine, and do not approve of putting the result of speculative reasoning as 

 experiment. 



While Faraday, similarly suspicious, as late as 1844, said: 



The word atom, which can never be used without involving much that is 

 purely hypothetical, is often intended to be used to express a simple fact. . . . 

 There can be no doubt that the words definite proportions, equivalents, primes, 

 etc., . . . did not express the hypothesis as well as the fact. 26 



The truth is that Dalton was a first-rate theorist, who arrived at his 

 conclusions, not primarily on the basis of induction from experiment, 

 but by reflection. Analogically, he imports the view of "matter" 

 peculiar to celestial mechanics, through molecular physics, into the 

 realm of chemistry. Proceeding thus deductively, he evinces little 

 awareness of the very complex problems involved, which the later devel- 

 opments of the atomic theory were to reveal. Cut off from the world, 

 he did not possess intimate acquaintance in detail with the labors of 

 his immediate predecessors and contemporaries — a happy accident, no 

 doubt. For, this freedom from puzzle and disturbance enabled him to 

 proceed boldly with a generalization when men of the caliber of Wollas- 

 ton and Davy hung back. Dalton had natural capacity for logical 

 thought, and complete confidence in the validity of those mathematical 

 syntheses of physical facts which he had pondered. 



But, as happens frequentty, his limitations are traceable to the same 

 source. Like Kant before him, Dalton became so entangled in the 

 theoretical ways of his own thought that, after he had promulgated his 



24 Manchester Memoirs, Vol. II. (2d series), pp. 287 f. 



25 Royal Institution Lecture Notes. 



26 " Experimental Researches," Vol. II., pp. 285 f. 



