LECTURE 1.] HISTORY OF CHEMISTRY. 9 



nation of this noted chemist. He says in effect : 9 If we 

 bring two lead balls of approximately equal weight into equili- 

 brium under water, on a balance, and then attach a piece of 

 cork (an object lighter than water) to one of the balls, this ball 

 will ascend ; it becomes, therefore, apparently lighter although 

 clearly we have increased the weight. A similar thing holds 

 in combustion; in this case we weigh in air; the metal the 

 compound of the metallic calx with phlogiston appears to be 

 lighter than the calx because the phlogiston, just like the cork, 

 is specifically lighter than the medium in which we weigh. I / 

 take it for granted that the reader perceives the fallacy in this 

 mode of regarding the matter ; and in this respect he is in^ 

 advance of the celebrated Macquer who could not with- 

 hold his admiration for this explanation. Even Boyle had 

 already observed that the metallic calces were specifically 

 lighter than the metals, but Guyton does not take this into 

 consideration ! 



As the reader will have observed, I have not hesitated to 

 call attention to the contradictions of the phlogiston theory, 

 and to its weakness with respect to any reasonably tenable 

 explanation of the increase of weight during combustion. In 

 spite, however, of those hazy conceptions, which constituted 

 the basis of the chemical opinions of the period, there were 

 men amongst the phlogistians who have scarcely been excelled 

 in the fertility of their discoveries by any of the chemists of the 

 present day. In this connection may I venture to make a 

 general statement? Am I not justified in asserting that falla- 

 cious theories are not always obstructive to the development of 

 science, and in supporting the view that it is better to possess 

 definite theoretical bases, even if they do not explain all the 

 facts, than to represent these facts themselves as the sole 

 triumphs of science ? Facts certainly play a great part in the 

 foundation and in the overthrow of a theory; indeed they 

 alone should have any influence in such matters; and if we 

 now turn our attention to the decline of the phlogiston theory, 



9 Kopp, Geschichte. 3, 149. 



