30 THOMAS STEERY HUNT ON A NATUEAL SYSTEM IN 



laboiirs of great naturalists have already nearly attained for the vegetable and animal 

 kingdoms." 



§ 1-1. " In approaching this great problem of classification, we have to examine, first, 

 the physical conditions and relations of each species, considered with relation to gravity, 

 cohesion, light, heat, electricity, and magnetism ; secondly, the chemical history of the 

 species, in which are to be considered its natvire 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 crys- 

 tal, is essentially quantitative. It is from all the above data, which would include the 

 whole physical and chemical history of inorganic bodies, that a natural system of mineral- 

 ogical classification is to be built up. . . . The variable relations to space of the 

 empirical equivalents of non-gaseous species or, in other words, the varying equivalent 

 volume (obtained 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 those bodies must be represented by formulas not less complex, 

 and with equivalent weights far more elevated than those usually assigned to the 

 polycyanids, the alkaloids, and the proximate principles of plants. To similar con- 

 clusions conduce also the researches on the specific heat of compounds." In the paper, 

 published in 186*7, from which the above extracts are taken, it was further said that the 

 views there set forth as " the basis of a true mineralogical classification " were not new, 

 but had been brought forward and maintained by the author in various publications 

 from 1853. 



§ 15. The starting point in this inquiry was the study of the chemistry of carbon. It 

 was in 1852 that I wrote, " we may define organic chemistry as the chemistry of the com- 

 pounds of carbon," ' a statement which though a common-place to-day was then perhaps 

 made for the first time. I then insisted upon what I called " the carbon series " and "the 

 silicon series," the latter including all known silicon compounds. This was followed in 

 1853 by an essay on " The Theory of Chemical Changes and Equivalent Volumes," ^ 

 wherein the question of equivalent or so-called atomic volumes was discussed with rela- 

 tion to the investigations of Playfair and Joule, and the speculations of Dana. It was 

 then and there suggested that " all species crystallizing in the same shape haA^e the 

 same equivalent volume, so that their equivalent weights (as in the case of vapors) are 

 directly as their densités, and the equivalents of mineral species are as much more elcA'a- 

 ted than those of the carbon series as the specific gravities are higher." 



^ 10. Another principle there set forth was the general application of the law of pro- 

 gressive or homologous series, first enunciated in 1842 bj^ James Schiel of St. Louis, and 

 soon afterwards adopted by Ch. Grerhardt, but hitherto applied only to hydrocarbonacous 

 or so-called organic species. It was now said that " it may be expected that mineral 



' Essay on Organic Chemistry, forming Part iv of the Principles of Chemistry by B. Silliman ; 3rd revised 

 edition, 1852, p. 378. 



2 Amer. Jour. Science, Marcli, 1853 (xv. 226-234) L. E. & D. Philos. Mag., (4) v. 526, and in German in the 

 Chemisches Centralblatt of Leipsic for the same year (p. 849) ; also in the author's Chem. and Geol. Es.says, 

 pp. 427-437. 



