1 74 MEMOIR OF DR. DALTON, AND 



In reading the first part of this question we suppose he 

 must live as a discoverer ; in reading the second part, we find 

 him timidly committing suicide. He wavers between his 

 theory and his experiments. If determinate proportion be a 

 law, he might have supposed it rigid, like other laws of 

 nature ; but he leaves a portion of the residue altered, so 

 that, after all, we only receive from him indeterminate, or 

 nearly determinate proportions. 



The experiment to which the question refers occurs in 

 p. 296. He draws no valuable conclusion from it. He says 

 also, p. 299, " In the combustion of charcoal with empyreal 

 air, the expenditure of the latter, in fixable air and water, 

 was always found to be more than thrice the weight of the 

 charcoal. I could now easily ascertain the proportion of 

 these, and even the quantity of the acid and phlogistic matter 

 in this and other bodies; but as my present purposes are 

 answered by approximation, I think it unnecessary to detain 

 the reader any longer on this subject." 



His principal object was to explain the nature of fire, which 

 he considers as subject to the laws of gravitation, and to be 

 the cause of the aeriform state of bodies. 



The only law in which be introduces numbers is the fourth 

 of his " primary notions of the matter of fire." " The 

 changes of repellent matter, by which attractive and gravi- 

 tating particles form elastic fluids, are distinct atmospheres of 

 fiery matter, in which the densities are reciprocally as the 

 distances from the central particles, in a duplicate or higher 

 ratio." * 



His writings are mostly in the first stage of thought before 

 opinion is formed. Commentators on such persons are obliged 

 to extend the ideas a little in order to make them clear, and 

 so the original writer gets credit for more than he had ever 

 done. Such writers are of great value when they lead towards 

 discoveries ; but we are apt to give them the entire honour when 



• Page 306. 



