190 REPORT 1860. 



pressed. In one of these, the addition of a crystal or two of chlorate of 

 potash to water at the temperature of 648° F., proved sufficient to prevent 

 any action of the aqueous vapour on the glass ; so easily was it saturated by 

 the presence of a more soluble material. 



Neither is it at all probable that any stratum which can be supposed to have 

 preceded granite under extraordinary conditions of heat and pressure, can 

 have resembled in any degree obsidian or glass. M. Daubree takes the 

 vapour expansion of the ocean over the globe as equivalent to a pressure 

 of 250 atmospheres, somewhat exceeding Mitscherlich's supposition before 

 quoted. On this pressure Mitscherlich, as has been said, sagaciously re- 

 marked, that it would probably materially modify the chemical affinities 

 of bodies, and prevent the formation of silicate of lime. His anticipation has 

 been experimentally verified ; and an equally remarkable instance of the 

 same principle has been lately observed by Mr. Gore, who has found, on 

 immersing some fifty substances in carbonic acid liquefied by pressure, that 

 in that state it is chemically inert, to such a degree as not to dissolve oxygen 

 salts. In these cases it should seem that pressure favours homogeneous, or 

 simple, at the expense of heterogeneous, or complex, attractions ; and there is 

 all the less reason for admitting M. Daubree's supposition, that obsidian, 

 or any vitreous silicates, preceded the granitic rocks. 



We may carry these ideas further ; Ave may extend our speculations from 

 the heat and weight of a vaporized sea to the gaseous system of Laplace, and 

 the ultimate atoms of Newton. Then, as the heat by degrees radiated into 

 space, and as the repulsive force yielded to the forces of attraction, the 

 first compounds would be of the simplest order, — water, and hydrochloric 

 acid, — the chlorides of potassium, sodium, silicon, and aluminium, the oxides 

 of magnesium and calcium, with others of a like class. Here we have both 

 the materials of the sea, and of the primary crust of the earth ; and at the 

 same time all the power of consolidation which free crystalline force and 

 enormous pressure can give to materials indisposed by that pressure to enter 

 into complicated combination. 



In contemplating the origin of granite, it is not, however, competent to 

 us to regard it as a fundamental rock only, since it preserves the same 

 crystalline character under various conditions of heat and pressure. But 

 we must remember that the gaseous theory which we are imagining implies 

 a residue, in an internal gasometer, of similar primary compounds confined 

 in a highly heated, condensed, and elastic state at no great distance under 

 our feet, from the sudden or gradual evolution of which it is not difficult 

 to conceive that all the eruptive rocks and veins, and many of the pheno- 

 mena of consolidation in the sedimentary strata, may be accounted for. 



Every rock of eruption, and every mineral vein, which has shot up into the 

 strata, indicates such an origin. The porphyries, trachytes, basalts, and lavas 

 are essentially chemical and crystalline compounds. They differ from the quart- 

 ziferous rocks only in this, that the chief part of the siliceous ingredients which 

 characterize the latter having been antecedently used up, the greater fusi- 

 bility of the former has more or less obliterated their crystalline structure. 



In these speculations it matters not from what source we suppose the 

 heat of the earth to have been derived. Perhaps, a law of gravity, together 

 with the other forces of attraction, imposed on the ultimate particles of 

 matter, may account for all the heat which is, or has been in the world. In 

 any case, the most probable inductive conclusion from our knowledge of 

 the earth's heat, and the phenomena of eruption, with the light thrown on 

 the production of minerals by Daubree's_/w-s£ series of experiments, and 

 those of Durocher, appears to be, that mineral veins and eruptive rocks 

 are the result of gaseous combinations and reactions. As regards mineral 



