Biography of Berzelius. 3 



positive constituents. But after Mitscherlich's discovery of 

 isomorphism, which has exerted so important an influence 

 upon the arrangement of the system, he considered it more ad- 

 vantageous to classify minerals according to their electro-ne- 

 gative constituents, because the substitution of isomorphous 

 substances is far more frequent among the bases than among 

 the acids ; and therefore the classification according to the 

 electro-negative constituents corresponded more with the 

 requirements of mineralogists. Both methods have their 

 advantages ; they are equally philosophical, and may be em- 

 ployed with equal justice ; it is therefore a great injustice that 

 Berzelius should have been charged with inconsistency in 

 making this alteration. 



The mineral system of Berzelius is not even yet completed. 

 He was far from wishing to affirm that it was incapable of 

 improvement, on the other hand, during his whole after-life 

 he continually improved it, and from time to time published 

 it in a more perfect form. The last edition was superin- 

 tended by Kammelsberg in 1847 at the request of Berzelius. 



The most important modifications still to be made on this 

 system, are perhaps those which would result from a more 

 simple application of the doctrine of isomorphism. It is cer- 

 tainly difficult to harmonize the opinions as to how this ought 

 to be done. 



Berzelius was not quite right in affirming that it is the 

 constituents of a substance alone which must determine 

 its place in a system. Even in the last " Jahresberichte" 

 published by him, he declares that, in a mineral system, the 

 sole question for consideration is the elements and their 

 inorganic combinations, and that it is these which must be 

 systematically arranged. But he himself directs attention 

 to the difficulties which this view necessarily involves. Is 

 it, he asks, admissible to make one species of diamond and 

 graphite, or of rutile, Brookite, and anatase, or of calcareous 

 spar and arragonite ? It is scarcely to be expected that mi- 

 neralogists will give their consent to such a course. 



However, Berzelius decides in the affirmative. Still I am 



of opinion that there are even many chemists who will not 



unconditionally agree with him in this. For it is not alone 



a2 



