CLASSIFICATION. 137 



the knowledge and practice of chemistry, in order to render them 

 practicable ;* mixed methods, where the order of the species is 

 made to depend partly upon the natural properties, and partly upon 

 their chemical constitution, t &c. 



nected, by a greater degree of similarity, with each other, than with 

 those of other classes. 



To give a recapitulation, in a descending order ; the mineral kingdom 

 contains three classes. Every class comprehends part of the series of 

 genera, collected into several orders. The classes are not of the same 

 extent ; and the orders which they contain are joined by an equal degree 

 of similarity. Every order is an assemblage of several genera in their 

 regular succession ; hence it is likewise a portion of the general series of 

 genera. The genera comprised within an order, present equal degrees 

 of similarity. Every genus is an assemblage of similar species ; it is an 

 unity in the series of genera. The species within the genera are con- 

 nected by equal degrees of similarity. Every species is an assemblage 

 of homogeneous individuals ; the individuals of a species are connected 

 by the series of characters, that is to say, by real natural transitions. 

 The individual is the simple mineral, produced by nature. It is the only 

 systematic idea which immediately refers to nature, or to which an object 

 of observation corresponds, 



It is to be observed, that none of these ideas have been obtained, or 

 deduced from the others, by means of a division. For, in order to arrive 

 at them, we have not begun with the highest, but with the lowest one, 

 which is that of the individual, and then the idea of the species has been 

 determined according to the idea of homogeneity, those of the genus, 

 order, &c. according to different degrees of natural, historical resem- 

 blance ; the whole of them, by aggregation or assemblage. Besides the 

 idea of a species, a division would have pre-supposed also that of the 

 mineral kingdom ; and it would have required a principle according to 

 which it might have been effected with consistency. The present treaN 

 ise will show that these conditions in fact may be fulfilled, yet such a di- 

 vision, it will appear, cannot afford the same classes, orders and genera, 

 which have been obtained by the other process, and the degrees of class* 

 ification which will be thus obtained, while they subserve a very im- 

 portant purpose, will be altogether inadequate to the purpose of giving 

 a general view of inorganic nature, in agreement with the similarity 

 which exists among its productions, which is the last and highest aim of 

 Natural History. 



Perzelius. t Abbe Hady. 



12* 



