Introduction to the Study of Mineralogy. 393 



fugitive shades which modify the varieties in botany, pre- 

 sent, from the different laws or' Nature, or from the different 

 ways in which she operates, results very dist.nct. In calca- 

 reous species, for example, the various crystalline forms, 

 stalactites, marbles, Stc, are so many modifications of one 

 and the same substance, which, without doubt, deserve to 

 be separately observed and studied ; and if in all these we 

 were not to see any thing but lime and carbonic acid, it 

 would be as if we contented ourselves with the inscription 

 of a picture equally interesting by the assemblage and by 

 the variety of its objects. 



On the other hand, it is evident that mineralogists have 

 really profited to a certain point, by the results of che- 

 mistry, in order to form the distributions which have been 

 designated by the term mineralogical methods : for without 

 speaking here of the use which they have made of certain 

 properties, such as effervescence with the acids, which is a 

 true chemical property, they never could have been able, 

 without the aid of analysis, to refer subsances to their true 

 classes. The carbonate of lead, commonly known us white 

 lead, was regarded as a species foreign to the metals, and 

 was probably arranged among the stones. In the Brisgaw, 

 a few years ago, there was found a crystallized substance 

 with small incrusted lamin2e, and of a white colour : mine- 

 ralogists had alternately regarded it as a zeolite, and as a 

 ponderous spar. The analysis of Pelletier, however, assigned 

 its true place, as being among the ores of zinc, by the name 

 of calamine. 



Chemistry ha-? therefore been, at least tacitly, the guide 

 of mineralogists in the determination of species ; and the 

 formation of the genera is really the point at which systems 

 in every respect begin to diverge. 



In those of the mineralogists, the species which compose 

 one and the same genus are connected with each other by 

 a character derived from some quality which is common to 

 them, or by several characters so combined that their as- 

 semblage is considered as belonging only to the collection 

 of the species in question. The genera adopted by cheuu^s 

 baye their foundation in analysis itself: they depend, as we 



have 



