'Reflections on some Miner alogical Systems, 297 



molecules are similar, and composed of the same elements 

 united in the same proportion. " It is the assemblage of 

 all the minerals which agree, with respect to the final re- 

 sults of division, in their physical and chemical molecules, 

 in the true expression of nature reduced to its greatest sim- 

 plicity*. 



This definition of the mineralogical species is rigorous, 

 and leaves noihing to be desired ; but it requires a know- 

 ledge of the integral molecules. In the first place, it re- 

 quires us to ascertain what its form is in all cases similar to 

 itself: in the second place, we must be able to determine 

 the nature and relations of its chemical elements. The first 

 problem consists in finding the planes which terminate the 

 small solid called the integral molecule, or, what amounts 

 to the same thing, a solid which may resemble it ; for it is 

 not the absolute but the relative dimensions of this mole- 

 cule which are required. But, the planes which terminate 

 this solid can be but those which are parallel to the different 

 directions in which a mineral is divisible without break- 

 insr, or what has been denominated the direction of the 

 cleavage. 



It is otherwise with the problem respecting the chemical 

 element. We know that there exist vacuums between the 

 molecules of bodies, and that even these vacuities are very 

 considerable : hence it is that foreign matters have so often 

 interposed themselves, and altered the sensible characters 

 of a group of molecules or of a mass. Suppose that all the 

 directions of the cleavage parallel to the planes which ter- 

 minate the physical molecule are ascertained. Whatever 

 may be the dimensions of the piece in which these direc- 

 tions are found, we have the representative of the mole- 

 cule ; but as these dimensions necessarily exceed those of 

 the molecule itself, it follows that the piece contains more 

 than one molecule, and hence foreign matters may deposit 

 themselves in the interstices. Hitherto chemistry possesses 

 only the means of distinguishing the simple parts which 

 compose the physical elements from those which are inter- 

 posed. Hence a source of uncertainty in the results of 

 chemical analysis j and, in order that it" may enjoy all the 



* Most assuredly this conception, even were it devoid of basis, would do 

 honour to the human intellect. Man is placed in the middle of the universe, 

 as if to contemplate the infinite space which surrounds him. On whatever 

 side he looks, — whether he contemplates those worlds whose volumes and 

 remote distances lire to him without measure, or whether he considers the 

 atoms which form them and the laws by which these atoms are united, — every- 

 thing is to him infinite, and begets in his mind that sentiment of sublimity 

 originating m a grandeur for which we have no expression. 



confidence 



