384 Reflections on some Mineralogical Systems, 



amines this specimen attentively and unprejudicedly, must 

 believe that the whole has been common carbonated lime, 

 which has been exposed to the action of a sulphuric or 

 other solution of iron, that the carbonate of lime has been 

 gradually dissolved, and yielded its place to the oxide of 

 iron, precipitated from its solvent by the double affinity of 

 the lime for the acid in the solution of iron, and the oxide 

 of this metal for the carbonic acid. The carbonated lime 

 has served as a matrix to the oxide of iron, and it is very 

 possible that the direction of the laminae in the way of 

 the great diagonals may be rendered more sensible by the 

 solution of the old and precipitation of the new molecules 

 which came to deposit themselves in this abode. If, how- 

 ever, I have admitted the existence of a ferriferous carbo- 

 nated lime, where there is no lime, it is because I have seen 

 petrified wood where there was no wood. 



But, in taking the first explmation.generally, it seems 

 that, far from making the case of which I have spoken the 

 subject of an objection, it is for chemistry to draw from it 

 the greatest possible advantage. A grand effort which yet 

 remains to be made, is to distinguish between mixtures and 

 combinations. Let us suppose a mass, A, composed of 

 any number of physical elements, which have for chemical 

 molecules the substances a ! b + c, and another mass, B, 

 the chemical elements of which may be m + n. It is de- 

 manded if a mixture or a combination shall take place in 

 putting the bodies A and B together? If by physical divi- 

 sion we find a molecule similar to the molecule A, another 

 similar to that of B, and that by ehemical division we found 

 the chemical elements (a + b + c \ m + n,) it is evident that 

 we have a mixture, Cut it we find a new molecule, C, 

 with the same chemical result (a -\- b + c + m A- n), we 

 have a combination. It is therefore for chemistry, en- 

 lightened by physical (or mechanical) division, to resolve 

 this great problem ; and it is to restrain its influence too 

 much to confine within the province of mineralogy, that 

 which may guide our researches over the whole of nature 

 or the material world. 



Let us lake one particular case, — the neutral tartrate of 

 potash. This salt, like all others, has a physical and che- 

 mical constitution peculiar to itself, i\', in, adding to it 

 tartaric acid in a quantity sufficient to convert it into acid 

 tartrate ol potash, and in submitting these two substances 

 to all the chemical means of combining them, we find the 

 same form of physical molecule in the one part, and the 

 form of the physical molecule of tartaric acid in the other; 



we 



