240 PROCEEDINGS OF THE AMERICAN ACADEMY 



ine, first, the physical conditions and relations of each body, considered 

 with reference to gravity, cohesion, light, electricity, and magnetism ; 

 secondly, the chemical history of the body, in which are to be consid- 

 ered its nature as elemental or compound, its chemical relations with 

 regard to other bodies, and these chemical relations as modified by 

 physical conditions and forces. The quantitative relation of one min- 

 eral (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 phys- 

 ical and chemical history of inorganic bodies, that a natural system of 

 mineralogical classification is to be made up. Their application may 

 be illustrated by a few points drawn chiefly from the history of certain 

 natural families. 



The variable relation to space of the empirical equivalents of non- 

 gaseous species, or, in other words, the varying equivalent volume ob- 

 tained by dividing their empirical equivalent weights by the specific 

 gravity, shows that there exist in different species very unlike degrees 

 of condensation. At the same time we are led to the conclusion that 

 the molecular constitution of gems, spars, and ores is such that these 

 bodies must he represented by formulas not less complex, and with 

 equivalent weights far more elevated than those generally assigned to 

 the poly cyanides, the alkaloids, and the proximate principles of plants. 

 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 be- 

 tween the equivalent weights of gaseous species and their specific gravi- 

 ties. The gas or vapor of a volatile body constitutes a species distinct 

 from that same body in its liquid or solid state, the chemical formula 

 of the latter being some multiple of the former, and the liquid and solid 

 forms themselves often constituting distinct species of different equiva- 

 lent weights. In the case of analogous volatile compounds, as the hy- 

 drocarbons and their derivatives, the equivalent weights of the liquid 

 or solid species approximate to a constant quantity, so that the density 

 of these species, in the case of homologous or related alcohols, acids, 

 ethers, and glycerides, is subject to no great variation. These non-gas- 

 eous species are generated by the chemical union (identification) of a 

 number of volumes or equivalents of the gaseous species, which num- 



