MancJiester Memoirs, Vol. Iv. (191 1), No. <>. ir 



Harden's view of the matter. "... The teachers are to 

 blame ... in allowing so many of their students to put 

 the " cart before the horse" as they do in connection with 

 the atomic theory. The idea seems to prevail that the 

 laws of chemical combination follow from the atomic 

 theory, whereas the laws of combination were established 

 first as the results of experiments, and the atomic theory 

 of Dalton provides an explanation of the facts."" 



It is, of course, begging the question to assume that 

 the matter is as simple as this. Everyone knows which 

 is the cart and which is the horse, and no one knows for 

 certain how Dalton's chemical theory arose. Again, one 

 may urge, that supposing the origin of the theory to be 

 a controversial matter, the Board of Education is not 

 called upon to take one side or the other, and indeed,, 

 might well avoid such topics in its examination papers. 



The matter, however, is no longer controversial, being 

 so far settled that the purely inductive view of the origin 

 is quite untenable. There is the objection to it in prin- 

 ciple, that it says nothing about Dalton's physical theory 

 to which W. C. Henry drew attention long ago, and 

 Roscoe and Harden recently. Besides, Roscoe and 

 Harden have advanced objections to it in detail, which 

 must be final to anyone who considers them.^" 



Reasons must now be offered for rejecting the 

 deductive account which Roscoe and Harden have 

 accepted. The gist of it is that Ualton fi^st satisfied 

 himself that the atoms of different gases have different 

 sizes, and then devised the chemical theor}\ This, 

 Dalton's own narrative, has already been quoted on p. 10. 

 He gave it seven years after the events which it relates, 

 and it is quite unsatisfactory. It does not condescend to 



" " Science Examinations," 1909, p. 119. Board of Education. 

 ^ " " New View of the Origin of Dalton's Atomic Theory,"' p. 2S. 



