400 Introduction to the Study of Mineralogy. 



changed the face of science, by arranging in genera and 

 species the acid substances, made choice of the acids for 

 characterizing the genera, and distinguished the species ac- 

 cording to the diversity of the bases united in succession 

 with one and the same acid. This method of classifying 

 seemed to be pointeu out by the course of their operations 

 alone. Oxygen being the acidifying principle, the common 

 generator of the acids would become, by this kind of univer- 

 sality, the primitive substance, the different combinations 

 of which with the different acidifiable bases we should first 

 consider: and by a natural consequence, the acids resulting 

 from these combinations would become, in their turn, the 

 general terms to which we should refer the classification of 

 the different and more compound substances of which they 

 form part. The activity and energy of those principles 

 which have so strong a tendency to unite themselves with 

 the earths, the alkalis, and the metallic oxides, and seemed 

 to rule over the combinations into which they entered, pre- 

 sented a new reason for assigning them the first place in 

 these very combinations in which they then formed the 

 principal part. But the mineralogist, whose object simply 

 is to apply the results of analysis to the works of Nature, 

 sees things in another point of view, and is necessarily led 

 to choose the most fixed principles, as the common ties of 

 the different species which ought to concur to the formation 

 of genera. 



In order to place this truth in its proper light, we may 

 remark that, among the metallic substances which form 

 one of the great divisions of the mineral kingdom, several 

 admit an acid into their composition : hence it results in 

 the first place, that, by giving the first rank to the acids, 

 we could not avoid associating together in one and the same 

 genus, on the one hand, carbonate of lead with carbonate 

 of lime and barytes; on the other hand, the sulphate of 

 iron with the sulphate of lime and that of magnesia ; and so 

 on with several other relations, in order to preserve the 

 unity of the genera. Besides, by reasoning from combusti- 

 bles, which frequently form part of the acids, as with these 



acids 



