LECTURE XL 



REASONS FOR THE ASSUMPTION OF THE DIVISIBILITY OF ELEMENTARY 

 MOLECULES FIXING OF THE MOLECULAR WEIGHTS, BY WILLIAM- 

 SON, BY MEANS OF CHEMICAL REACTIONS THEORY OF THE 

 FORMATION OF ETHER FUSION OF THE RADICAL THEORY WITH 

 DUMAS' TYPES SUBSTITUTED AMMONIAS POLYATOMIC RADICALS 

 GERHARDT'S THEORY OF TYPES AND SYSTEM OF CLASSIFICATION. 



IT has often been stated that chemistry should advance by 

 development from within itself alone, and that the influence of 

 the other sciences is injurious if it is exerted in any other direc- 

 tion than that in which chemical facts appear to lead us. I 

 understand perfectly well that in chemistry a theory is not 

 chosen which is in contradiction to certain facts, in order to 

 attain a more complete agreement with physical laws, and I 

 appreciate this from the didactic point of view in particular ; 

 but I consider it just as proper and essential in our science to 

 modify our views so as to produce harmony with recognised 

 natural laws, and also with theories and hypotheses, as soon as 

 the facts permit of our doing so. It therefore appears to me 

 appropriate, now when in our historical development we have 

 arrived at the middle of a far-reaching reform }/ to advance some 

 of the not exclusively chemical reasons which told in favour of 

 the system of Laurent and Gerhardt. In doing this, I confine 

 myself to facts which appear to support the divisibility of the 

 molecules of the elements, for the special reason that this 

 hypothesis, even after it had been repeatedly announced, still 

 met with no approval. 



Amongst the results, of extreme value in chemistry, which 

 Favre and Silbermann announced in 1846 in their research on 

 heats of combustion, 1 there is a very remarkable fact which 



1 Comptes Rendus. 23, 200, 



