Reflections on some Miner ah glcal Systems, 301 



are found in the argillaceous or clay genus of Werner, of 

 which we are ignorant, and perhaps for ever shall be ig- 

 norant, to hovv"niany simple species they owe their origin. 

 What do we know of the family of argillaceous schist, of 

 serpentine, of pierre ollaire [potstone, Jameson ; talc o/- 

 laire, Haiiy, and serpentine ollaire, Brogniart], of pipe-clay, 

 and of fuller's earth ; except that we do not conceive why 

 they have been made strictly species? Whenever a mineral 

 gives no true representative of the species, and that we do 

 not there find other physical or chemical properties to re- 

 fer it with sufficient certainty to any whatever, in which it 

 may be strictly admissible, it is better to make it a species 

 of convention, in order to complete the outline which na- 

 ture has traced. 



DISTINCTION BETWEEN MINERALOGICAL SPECIES. 



In this point of view, the species of the mineral kingdom 

 should be divided into four sections, corresponding with 

 the four conditions of which I have already spoken. The 

 first should contain the species strictly so called (especes de 

 rigu'eur); the second, those by analogy; the third, those 

 which I call geognostic ; and the fourth, those of conven- 

 tion. All belong to nature ; the first only appertains to 

 science, if we wish to preserve to this word that idea of 

 rigour which it necessarily carries with it. 



The principle of M. Haiiy embraces all those which are 

 known in the first section, therefore this system embraces 

 all the mineralogy which is capable of beeoming a science. 



The method of M. Werner extends to all the mineral 

 kingdom. il Who embraces too much, badly binds," it is 

 said: thus we know not what is a species, because all are 

 species. We have a measure without unity. 



I pretend not that the system of mineralogy should 

 be subjected to the division indicated by these four sec- 

 tions; but if we wish to consider the bodies which com- 

 pose this kingdom with respect to the rank which they 

 ought strictly to occupy, we can no longer divide them 

 otherwise ; and even in classing them according to more 

 essential principles, it would not be useless to mention this, 

 in order that each individual may be estimated at its just 

 value. 



The advantages that mineralogy has derived from the 

 philosophic spirit which directed the researches into the 

 true type of the species, and the happy application of an 

 exact method of determinating it, have been immense. All 

 at once it is become a science ; it is supported by fixed 



principles 



