36 T. STERRY HUNT ON THE GENETIC 
crust. Against this latter explanation it is to be urged that, as we have endeavored to 
show, the successive groups of stratiform crystalline rocks which have been laid down on 
the pre-gneissic granite, and even this primeval granite itself, are not igneous but aqueous 
in origin, so that the exoplutonic hypothesis itself is untenable. The amount of plutonic 
extravasation in pre-Cambrian times was apparently small. 
§ 66. The crenitic hypothesis, however, admits a transfer of matters from below 
upward, in a state of solution, and the building-up from them, upon the solid floor of 
igneous rock, of the granite and all the succeeding crystalline schists, as in the scheme of 
the exoplutonists. This new aqueous hypothesis thus offers, it is believed, for the first 
time, a reasonable and tenable explanation of the universal corrugation of the oldest 
crystalline strata. The earth, according to this hypothesis, although intensely heated, had 
not, even at the early time when the waters were first condensed on its surface, a liquid 
interior, but was solid; and its crust is supposed to have presented no variations in com- 
position, except such as might result from crystallization and eliquation in a purely igneous 
congealing mass. The superficial quartzo-feldspathic or granitic layer, which is believed 
to overlie everywhere the quartzless basic doleritic rock, did not then exist, but has since 
been derived by crenitic action from the primary plutonic layer. This granitic stratum is, 
however, itself still subject, like the basic stratum beneath, to softening under the combined 
influences of water and heat, and to extrusion in the forms of eruptive granite and trachyte ; 
although it is less fusible, and, consequently, less susceptible of differentiation by eliqua- 
tion. It is, moreover, at the same time, less liable to alteration by lixiviation, from the 
fact that it is not a mass cooled from igneous fusion, but one deposited from water at com- 
paratively low temperatures, and thus lacks the porosity which belongs to the original 
plutonic stratum. 
§ 67. The upward transference of the vast and unknown quantity of material con- 
stituting the ancient granitic and gneissic rocks, which are at least many miles in thickness, 
and the contraction of the plutonic substratum, diminished by the removal of this great 
mass, would necessarily result in great movements of subsidence, with plications and frac- 
tures of the gneissic strata. We are, of course, ignorant whether these processes went on 
to a uniform degree over the whole surface of the earth, and whether similar conditions of 
thickness, and similar corrugations exist in those great portions of the eozoic crust which 
are concealed beneath the ocean’s waters, and beneath accumulations of newer strata. It 
may well be that the plication of the ancient granitic crust was, as in the case of younger 
stratified rocks, limited to certain areas. It can only be affirmed, in the present state of 
our knowledge, that in the relatively very small areas of the oldest gneissic rocks known 
to us, this plication is great and apparently universal, diminishing, however, materially in 
degree in the younger gneissic series. 
§ 68. Within the fractures and rifts of the ancient gneissic strata resulting from these 
great movements, the products of the uninterrupted crenitie process would henceforth be 
deposited, filling them with masses closely resembling those of the enclosing strata. 
Repetitions on a smaller scale of those movements would give rise to newer fissures inter- 
secting alike these strata and the first-deposited vein-stones, in the manner shown in our 
studies of the Laurentian rocks, where the process which produced the original quartzose, 
feldspathic, and calcareous deposits of the series was repeated at least twice, giving rise to 
primary and to secondary vein-stones mineralogically very similar to the first-formed or 
