206 7.8. Hunt on the objects and method of Mineralogy. 
mology, we find a ready and natural explanation of those vari- 
ations, within certain limits, occasionally met with in the compo- 
sition of certain crystalline silicates, sulphids, etc., from which 
some have conjectured the existence of a deviation from the law 
of definite proportions, in what is only an expression of that law 
in a higher form. 
The principle of polymerism is exemplified in related mineral 
species, such as meionite and zoisite, dipyre and jadeite, horn- 
blende and pyroxene, calcite and aragonite, opal and quartz, in 
the zircons of different densities, and in the various forms of 
titanic acid and of carbon, whose relations become at once intel- 
ligible if we adopt for these species high equivalent weights and 
complex molecules. The hardness of these isomeric or allotro- 
pic species, and their indifference to chemical reagents, 1 
with their condensation, or in other words, varies inversely as 
mineral species, and has then endeavored, by conjectures as to 
the architecture of crystalline molecules, to establish relations 
= whose significance I have here endeavored to set forth. 
exemplifying my notion of some of the principles which must 
orm the basis of a true mineralogical classification. 
