254 HISTORY OF MINERALOGY. 



intimate constitution and their external attributes. 

 Thus our mineralogical classification must always 

 have an eye turned towards chemistry. We can- 

 not get rid of the fundamental conviction, that the 

 elementary composition of bodies, since it fixes their 

 essence, must determine their properties. Hence 

 all mineralogical arrangements, whether they pro- 

 fess it or not, must be, in effect, chemical; they must 

 have it for their object to bring into view a set 

 of relations, which, whatever else they may be, are 

 at least chemical relations. We may begin with the 

 outside, but it is only in order to reach the inner 

 structure. We may classify without reference to 

 chemistry ; but if we do so, it is only that we may 

 assert chemical propositions with reference to our 

 classification. 



But, as we have already attempted to show, we 

 not only may, but we must classify, by other than 

 chemical characters, in order to be able to make our 

 classification the basis of chemical knowledge. In 

 order to assert chemical truths concerning bodies, 

 we must have the bodies known by some tests not 

 chemical. The chemist cannot assert that arragonite 

 does or does not contain strontia, except the mine- 

 ralogist can tell him whether any given specimen is 

 or is not arragonite. If chemistry be called upon to 

 supply the definitions as well as the doctrines of 

 mineralogy, the science can only consist of identical 

 propositions. 



Yet chemistry has been much employed in 



