2 Joseph LeConte—Genesis of Metalliferous Veins. 
nabar as well as other metallic sulphides are now being 
deposited there along with silica, from solutions. And yet so 
strong is the prejudice in favor of the sublimation theory for 
this sulphide, that Rolland after examining the phenomena of 
Sulphur Bank, after recognizing the complete saturation of all 
the rocks and earth with the up-coming solfataric waters and 
even truly describing oN occurrence of the cinnabar in recently 
«deposited silica in such wise that the two must have been 
- deposited from the same DEAERLE Soe talks vaguely about 
vapors and emanations of mercur 
Admitting them as bec biatiad: ‘the view that metalliferous 
veins have been deposited from solutions, the most difficult 
questions still remain. What are the conditions under which 
deposit takes place? nd what in addition to simple water 
have been the solvents? 
Conditions of deposit.—In answering this first question it must 
be remembered that the chemistry of nature is far more subtle 
and refined than that of the laboratory—that substances which 
are regarded as practically insoluble in the latter cannot be so 
regarded in the former. The infinite patience of nature and 
the infinite slowness of her operation must be taken into 
account. In the perpetual circulation of subterranean waters 
infinitesimal deposits, continued and accumulated through 
almost infinite time, produce large results. Thus mineral veins 
may be composed of substances of extremest insolubility and 
yet be deposited from solutions. In fact such extreme insolu- 
bility, or at least very feeble solubility would seem to be a 
condition of mineral vein formation, for otherwise the materials 
would in most cases be brought to the surface instead of being 
deposited below. 
it must be borne in mind that solubility, even the 
heat, in increasing’ solubility, is universally recognized; but 
pressure is usually regarded only as a on, condition of 
super-heat, and not as itself an active agent. But, in fact, 
ressure acts not only” indirectly as a sqnion of super r-heat, 
but also directly as an active agent in increasing the solubility 
of nearly all substances. Mr. “Sorb byt has not only proved this 
by actual experiment on a great variety of substances, but has 
shown that it is a necessary consequence and beautiful illustra- 
tion of the law of correlation and conservation of natural forces, 
and that we have in this as in the case of fusibility an example 
of the equivalency of iacchaical and molecular forces. For as 
in the matter @ ea in all cases in which expansion takes 
nnales des Mines, xiv, 384, 1878. 
; Poe Royal Society, vol. xii, p. 538, 1863. 
