112 The American Geologist. August, i89i 
the primeval surface under a pressure estimated to be equal to 250 
atmospheres, corresponding to a temperature near that of redness. 
This process Hunt regards as prior to that in which the actual 
crystalline rocks were formed, their mineralogical characters and 
associations being incompatible with the elevated temperature sup- 
posed. This early history was but a preparation for the generatiou 
of the crytalline schists, whose temperatures must have been such 
as to allow the existence of organic forms, evinced by Eozoon, b}' 
limestones, quartzytes, carbon, etc. 
These ditticulties show that no previous hypothesis meets all the 
conditions. The author therefore proposes the Crenitic Hypothesis. 
In the author's mind this hj-pothesis has been a gradual growth, 
its various stages of advance being recorded in his successive pub- 
lished papers, since 1858. It " conceives the ci*ystalline rocks to 
have been derived, directly or indirectly, by solution from a primar}- 
stratum of basic rock, the last congealed and superficial portion of 
the cooling globe, through the intervention of circulating subter- 
ranean waters, b}' which the mineral elements were brought to the 
surface. * * * Tljg cooling of the surface of the 
earth by radiation, and the heating from below, would establish 
in the disintegrated, porous and unstratified mass of the primary 
[basic] laj-er, a system of aqueous circulation, bj' which the waters 
penetrating this permeable layer would be returned again to the 
surface as thermal springs charged with various matters, there to 
be deposited. The result of this process of upward lixiviation of 
the mass would be the gradual separation of the primary, undiffer- 
entiated la3er into an upper stratum, consisting chiefl}' of acidic 
silicates, such as feldspars with quartz, and a lower, more basic 
and insoluble residual stratum charged with iron oxide and mag- 
nesia, the two representing respectively the overlying granitic and 
the underhing la^'ers, the presence of which beneath the earth's 
sui'face has generally been inferred from exoplutonic phenomena." 
The fundamental fact of this hypothesis is the formation, bj' 
aqueous secretion, of zeolitic minerals in the cavities of basic 
eruptive rocks. This is pursued in its ramifications and modifi- 
cations until it is found that orthoclase, quartz, albite, amphibole, 
garnet, epidote, magnetite, hematite, native copper, native silver, 
and in fact nearly all the minerals that are found in the gneisses 
or in schists, and many others, are explainable b}' aqueous secre- 
tion from basic plutonic rocks. 
The argument is pushed to its conclusion with a wealth of il- 
