222 CONTRIBUTIONS TO MICRO-MINERALOGY. 



Kingdom should embrace the physiography and classification 

 of all inorganlzed bodies ; and although the sphere of inquiry 

 would be thus greatly extended beyond the limits originally 

 comprehended under the term Mineralogy, yet that term 

 might be retained with a conventional significance implying 

 the Natural History Method of inquiry, which embraces a 

 consideration of all the characters common to inorganic bodies, 

 in contradistinction to the strictly Chemical Method. In this 

 conventional use of the term Mineralogy for a wider sphere of 

 inquiry, I am supported (though from another point of view) 

 by Professor Fleming of Edinburgh.* 



The Mineral Kingdom would then be naturally divided 

 into two broad and great divisions, viz. : — 



I. HoMOGENiA, embracing Minerals proper, and 



II, Heterogenia, including bodies of definite chemical 



composition, but of composite structure — as Coal, 

 Bergmehl, &c. — Mechanical mixtures of chemical con- 

 stituents, but of apparent homogeneous aspect, as 

 Obsidian — and Erupted, Sedimentary, Metamorphosed, 

 Conglomerated f aggregates of mineral matter, com- 

 prising Rocks proper. 



And here it may be necessary to define my idea of the 

 Mineral Individual. This, as most Mineralogists are agreed, 

 is the crystal state, which implies a definite chemical com- 

 position in the constituting mass. But we have other forms 

 of matter to deal with, which must find a place in our 

 Systems : these are the amorphous, liquid and vaporiform con- 

 ditions of the same chemical body ; which states 1 regard, for 

 convenience of description, if not for more logical reasons, as 

 analogous to the metamorphic or embryonic stages of the 

 lower forms of animals ; and as Zoologists now regard the 

 whole cycle of Metamorphism or Development to be neces- 

 sarily comprised in the description of the Animal Individual, so 

 do I conceive the vaporiform, liquid, and amorphous states of 

 the same body, as only requiring favourable conditions to be 

 developed into the perfect form or crystal state, to represent 

 the series of the Mineral Individual. Thus, steam by con- 

 densation passes into water ; water, at a certain temperature, 

 passes into the amorphous or crystal state according to cir- 

 cumstances ; in the latter case it is Hexagonal Ice — the 

 perfect Mineral Individual of the series. This, perhaps, is 



* On the different Branches of Natural History, &c. ; an Address to the 

 Natural History Section of the British Association at Glasgow, 1855 : 

 Edinburgh New Phil. Journal, No. 5, New k-!erica, pp. 180-2. 



t Vide Humboldt's Cosmos, by Sabine, vol. i., p. 236. 



