432 SCIENCE PROGRESS. 



accepted at the present day as the basis of any scientific 

 scheme of classification, and with its introduction the 

 older views have almost entirely passed into oblivion. 



Here again Dana's mineralogy accurately represents 

 the progress of events. Rose's Krystallo-chemisches 

 System, which is generally taken as the starting point of 

 the newer methods, was published in 1852 ; but already in 

 his third edition (1850) Dana, who was always ready to 

 grasp after right methods and to sacrifice personal predilec- 

 tion, had dropped the old system entirely. In the preface 

 to that edition the following remarkable words occur : 

 "To chano-e is alwavs seeming fickleness. But not to 

 change with the advance of science is worse ; it is per- 

 sistence in error; and, therefore, notwithstanding the former 

 adoption of what has been called the Natural History 

 System and the pledge to its support given by the author 

 in supplying it with a Latin nomenclature, the whole 

 system, its classes, orders, genera, and Latin names have 

 been rejected, and even the trace of it which the 

 synonymy might perhaps rightly bear has been discarded." 



Principles similar to those which guided Rose had been 

 previously laid down by Hausmann and Fuchs, but were 

 less completely elaborated. Rose himself had been clear- 

 ing the way towards this end for twenty years ; but the third 

 edition of Dana's System set the seal upon the new 

 departure, and from that date modern views upon mineral 

 species may be regarded as firmly established. We hear 

 little more of orders and genera; minerals which are 

 closely allied are brought together into groups ; those 

 which deviate only slightly and in unimportant respects 

 from a normal type retain their trivial names, but are only 

 regarded as "varieties"; and, finally, all the different 

 minerals and mineral groups, which for the most part show 

 very slight resemblances one to another, are classified in a 

 somewhat disjointed manner by their chemical composition, 

 the purely chemical arrangement being only so far modified 

 as to bring together those which are " isomorphous," i.e., 

 which with analogous composition exhibit also a close 

 similarity of form. 



