On Crystallography, \§1 



principal specie?, because they admit of the existence, at 

 least in part, of the predominant characters. If this was 

 not the case, they ought no longer to occupy a place in the 

 method: they ought to be thrown into the general appen- 

 dix, in which are placed the mixed substances called rocks. 

 And this shows how contrary it is K) the spirit of the me- 

 thod, to place on the same line (as so many particular 

 species) with the true species, marles, argils, schists, and 

 other bodies, which are only fortuitous aggregates of species 

 already classed in other places in the method, and no one 

 of which imprints its character on the whole; so that we 

 are even unable to decide to what species they ought to be 

 referred, as being but a simple appendage. 



From all that I have said, we shall easily conceive how 

 important it would be to determine by the aid of analysis, 

 (with respect to each species) those principles which concur 

 by themselves to the formation of the integrant moleculcj 

 by operating on picked pieces, the composition of which 

 contains only what cannot be dispensed with, without ceasing 

 to be what it really is, and which had borrowed nothing, if 

 we may be allowed the expression, from the liquid in which it 

 had originated. We should thus have the Tnnit from which 

 the analyses of other pieces remove more or less, according 

 as the latter contain principles purely accidental, or if one 

 of the constituent principles i« found there in excess. 

 This limit would give what would be called the analysis of 

 the mineral submitted to experiment, and the other results 

 would make known the accidental diversities of which the 

 composition is susceptible : they would serve to indicate 

 to what term a certain principle has varied in its propor- 

 tions, and to unveil the principles which have only a trans- 

 itory existence, and are rather a surcharge with respect to 

 the nuneral which contains them, as they do not contri- 

 bute to its huegrity. 



I think I have sufficiently shown how much strength 

 may be acquired by chemistry and mineralogy by their 

 mutual cooperation. Without the former we should be 

 ignorant in what class a mineral ought to be placed if it 

 contains an acid, or if earths only enter its composition, 

 or if it does not conceal a metallic substance under the ap- 

 pearance of a simple stone. Without the latter art, it 

 would frequently be difficult to refer to the type of the 

 species the varieties which appertain to it. The one indi- 

 cates the first link of the chain, and marks the point to 

 which it ought to be attached ; but the intervention of the 



N 3 other 



