XIX.] OBJECTS AND METHOD OF MINERALOGY. 455 



give to mineralogy a natural system. "With similar views as to 

 the scope of the science, and with far higher and juster con^ep- 

 tions of its method, Stallo, in his Philosophy of Nature, has 

 touched the questions before us, and has attempted to show 

 the significance of the relations of the metals to cohesion, grav- 

 ity, light, and electricity, but has gone no further. 



In approaching this great problem of classification, we have 

 to examine, first, the physical condition and relations of each 

 species, considered with relation to gravity, cohesion, light, 

 heat, electricity, and magnetism; secondly, the chemical his- 

 tory of the species, in which are to be considered its nature, as 

 elemental or compound, its chemical relations to other species, 

 and these relations as modified by physical conditions and 

 forces. The quantitative relation of one mineral (chemical) 

 species to another is its equivalent weight, and the chemical 

 species, until it attains to individuality in the crystal, is essen- 

 tially quantitative. 



It is from all the above data, which would include the whole 

 physical and chemical history of inorganic bodies, that a nat- 

 ural system of mineralogical classification is to be built up. 

 Their application may be illustrated by a few points drawn 

 from the history of certain natural families. 



The variable relations to space of the empirical equivalents 

 of non-gaseous species, or, in other words, the varying equiva- 

 lent volume (obtained by dividing their empirical equivalent 

 weights by the specific gravity), shows that there exist in differ- 

 ent species very unlike degrees of condensation. At the same 

 time we are led to the conclusion that the molecular constitu- 

 tion of gems, spars, and ores is such that those bodies must be 

 represented by formulas not less complex, and with equivalent 

 weights far more elevated than those usually assigned to the 

 polycyanides, the alkaloids, and the proximate principles of 

 plants. (Ante, pages 434 and 441.) To similar conclusions 

 conduce also the researches on the specific heat of compounds. 



There probably exists between the true equivalent weights 

 of non-gaseous species and their densities a relation as simple 

 as that between the equivalent weights of gaseous species and 



