2^ Professor Necker on Miiiercilogy considered 



serving unsullied by ^ heterogeneous mixture, a method which 

 must confine itself to simple, pure, complete, and perfect indivi- 

 dual beings. 



§ 45. We now begin our account of the divisions of the clas- 

 sification, by ascertaining accurately the nature of the more im- 

 portant among the lowest of these divisions, that is the species. 

 We have already noticed that this problem has been always a 

 field of contention among mineralogists. Tacitly agreeing, as it 

 appears upon one point, that the abstract ideas of substance or 

 chemical composition, were to be the subjects they had to arrange 

 on their classification, they seem also to have agreed that all 

 bodies of the same chemical composition, or similar in their sub- 

 stance, should be considered as belonging to the same species, 

 and the dispute was merely about which of the chemical, the 

 physical, or the external characters, were the surest, the readiest, 

 or the most convenient means of ascertaining differences or simi- 

 litudes of chemical composition in minerals. 



Under the idea that substance was the chief object of conside- 

 ration, it is not to be wondered that the various forms and phy- 

 sical qualities which any substance could assume, should have 

 been regarded as unimportant, unessential, and, as it were, 

 merely accidental attributes, and that such accidents would 

 have been looked upon as mere varieties of definite species ; 

 though it appears to us rather difficult to understand how form 

 could ever be considered as a variety of substance. 



§ 46. Very different will be our point of view when we are 

 to class, not abstract ideas, but real and positive individuals, in 

 which form as well as other physical properties are as essential 

 attributes as chemical composition. Here we will find ourselves 

 on the same ground with the zoologists and botanists, who com- 

 pare together their various animal or vegetable individuals, and 

 we will proceed in conformity with their principles. 



§ 47. Their object in collecting all the individuals in a cer.^ 

 tain number of groups, of which the lowest are comprised in the 

 highest, is to assemble together those beings which resemble 

 each other more than they resemble those of other species, 

 genera, order, classes. Such a definition is applied to spe- 

 cies in regard to other species, to genera and orders in regard 



