UISTORY OF THE ATOMIC THEORY. 229 



§ 61. " This general law is subject to an exception also, 

 when there is a change of the aggregate condition during the 

 action of two or more substances, and in this case also a com- 

 bination takes place of a fixed proportion." 



Here we have a clear account of the direction that Ber- 

 thoUet's teachings gave, and the consequences are logically 

 deduced. Here, too, we find that fixed proportions are 

 obtained as exceptions, but it is also seen how needful it was 

 to have them occasionally in order to explain facts in the 

 science. 



Stromeyer's words do, in fact, represent the confused and 

 contradictory opinions of the time, and afford us another proof 

 that no one before Dalton had given opinions sufficiently 

 authoritative on the atomic theory to be retained by the 

 teachers of chemistry ; and we may add also, none deemed 

 of sufficient importance to demand at the time very serious 

 discussion. 



This want of attention, even to imperfect theories, arose 

 mainly, I believe, from the fact, that those theories hitherto 

 given had not had accumulative scientific proof to give them 

 force in the world ; they had organized no executive force. 

 Chemists, generally, had not arrived as far as the inquiries 

 already quoted. 



It was intended to give a number of similar instances, to 

 show how entirely all atomic theories and theories of definite 

 proportions were out of the boundaries of general chemical 

 science when Dalton published. I happened to take up 

 Stromeyer first; many instances occur in our own country, 

 but this will probably be found sufficient. 



