326 



But cannot this be renietlieJ, not deterniination and description 

 in every branch of Natural History in analogous studies ruled by the 

 same laws and following the same description ] Why should the 

 method be otherwise in mineralogy'? I know not, but I know that it 

 is otherwise. The scientist who wishes to classify and describe a new 

 mineral, always makes an analysis of it ; but the mineralogist who 

 afterwards meets that same mineral, tries to find the species to which 

 it belongs just by the external" characters and a few blowpipe tests which 

 cannot suffice to find the species, since they were not deeuied sufficieilt 

 to constitute it. 



Chemical composition, together with the crystalline form, is the 

 basis of classification, therefore it ought to be also the ground for 

 determination. But chemical composition cannot be ascertained without 

 analysis, therefore a true chemical analysis must be the fundamental 

 operation in determining minerals. All other observations and experi- 

 ments ai'e useful only in as much as they indicate either the composition 

 of the mineral or the habit of the crystal. 



Let us now apply this principle practically. You all know that 

 ia analytical chemistry substances are grouped according to the 

 elements which they contain. These elements thems?lves are classed 

 according to the solubility of their salts. A first series of tests leads 

 you to one of the great classes of elements, the second points out, one 

 by one, each of the elements that enter into the composition of the sub- 

 stance un.'ler examination. Now, I would distribute the different 

 species of minerals according to the order in which a properly con- 

 ducted chemical analysis would reveal them. This, of c:u'se, ought 

 well to answer every case if we suppose in the student the time and 

 ability for making a quantitative analysis ; but such cannot ordinarily 

 be the case, and the distinction must be maintained between the com- 

 )ilete analysis of a mineral and its mere determioation. 



But when the qualitative analysis has restricted a specimen to a 

 limited group, there is nothing to prevent us from using crystalline 

 form and physical characters to reduce it to the last species. Dy so 

 doing we re-establish the logical order which is invertel in the actual 

 system. For it is an admitted principle that those properties which 

 are most essential must be employed to determine the classes; less abso- 



