512 THE POPULAR SCIENCE MONTHLY 



theory, he stopped short in middle life, and could not appreciate the 

 work of others who followed and supported him. This is the blot on 

 his 'scutcheon. Still, even so, we must hold the balance true. The 

 kinetic doctrine of " matter," integral to the Cartesian philosophy, had 

 paled before Newtonian atomism. And Dalton had grasped Newton's 

 view so logically that he could not admit the law of equal volumes, 

 because, as he held, " no two elastic bodies agree in the size of their 

 particles." The very success of his hypothesis blinded him to Gay- 

 Lussac's experimental evidence — it would not conform to the conceptual 

 scheme. As he wrote to Berzelius, in September, 1812 : 



The French doctrine of equal measures of gases combining, etc., is what I 

 do not admit, understanding it in a mathematical sense. At the same time 

 I acknowledge there is something wonderful in the frequency of the ap- 

 proximation. 27 



Of course, the fact was that, as Wurz points out, 



The relation which exists between the densities of gases and their atomic 

 weights is not so simple as we should at first sight be led to expect, and as for 

 a long time it was thought to be. 28 



Nay, " understanding it in a mathematical sense," Dalton had his 

 reasons. By a kind of paradox, the very simplicity of his notion 

 befogged him here, just as the problems bred of the atomic theory 

 diverted chemists for many a long day from the study of affinity. 



We may conclude, then, that the logical character of Dalton's mind 

 enabled him to formulate the timely conceptual representation on which 

 chemical logic has pivoted ever since; that his numerical conception 

 has stood the test of further discovery better than most hypotheses; 

 and that, little as he knew it, or could admit it at the moment, he laid 

 the foundation for that intimate alliance between physics and chemistry 

 which forms one of the most pregnant among contemporary movements. 

 For, the active criticism of the atomic theory — that it dogmatizes about 

 the physical constants marking the differences between the elements, 

 that it reveals little or nothing of the processes incident to chemical 

 composition and destruction, that it neglects synthesis — testifies also, 

 if negatively, to the revolution wrought by its author. Pity is akin to 

 praise here. And to-night, as we celebrate Dalton's " thoughts that 

 breathe," we are bound to let praise have its free way, especially when 

 we contemplate the indomitable devotion of a character who, amid sore 

 difficulties, but furnished with the splendid spur of consecration to the 

 ideal, achieved so much for man's conquest of the secrets of nature. 



27 The italics " understanding," etc., are mine. 



28 "The Atomic Theory," p. 35 (English translation). 



