OF ARTS AND SCIENCES : JANUARY 8, 1867. 241 



ber varies inversely as the density of the latter species. It follows from 

 this, that the equivalent weights of the solid and liquid alcohols and fats 

 must be so high as to be a common measure of the vapor-equivalents 

 of all bodies belonging to the above-named series. The empirical for- 

 mula Cii4 Hjio Oi2, which is the lowest one representing the tristearic 

 glyceride, ordinary stearine, is probably far from representing the true 

 equivalent weight of this fat in its liquid or solid state ; and if it should 

 hereafter be found that its density corresponds to six times the above 

 formula, it would follow that the equivalent of liquid acetic acid, whose 

 density differs but slightly from that of fused stearine, must have a for- 

 mula and an equivalent weight about one hundred times that which we 

 deduce from the density of acetic acid vapor. C4 H4 O4. 



Starting from these high equivalent weights of hquid and solid hydro- 

 carbonaceous species, and their correspondingly complex formulas, we 

 are prepared to admit that other orders of mineral species, such as oxides, 

 silicates, carbonates, and sulphides, have formulas and equivalent weights 

 corresponding to their still higher densities, and we proceed to apply to 

 these bodies the laws of substitution, homology, and polymerism, which 

 have so long been recognized in the chemical study of members of the 

 carbon series. The formulas thus deduced for various native silicates 

 and carbon-spars show that these polybasic salts may contain many 

 atoms of different bases, and their frequently complex constitution is 

 thus explained. In the application of the principle of chemical homol- 

 ogy we find a ready and natural explanation of the variations, within 

 certain limits, occasionally met with in the composition of certain crys- 

 talline silicates, sulphides, etc., from which some have conjectured the 

 existence of a deviation from the law of definite proportions in what is 

 but an expression of that law in a higher form. The principle of poly- 

 merism is exemplified in related mineral species, such as meionite and 

 zoisite, dipyre and jadeite, hornblende and pyroxene, calcite and arra- 

 gonite, 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 intelligible if we adopt for these species high equivalent weights 

 and complex molecules. The hardness of these isomeric or allotropic 

 species and their indifference to chemical agents increase with their 

 condensation, or in other words vary inversely as their empirical equiv- 

 alent volume, so that we here find a direct relation between chemical 

 and physical properties. 



It is in these high chemical equivalents of the species, and in certain 



VOL. VII. 31 



