3G6 
THE GEOLOGIST. 
the movement, and in planes perpendicular, or rather diagonal, to the 
opposite pressures — the different crystalline elements separating into 
more or less distinct bands or laminje, according as their forms 
permitted them to move ■with greater or less freedom. The silex, if in 
a gelatinous condition, would possess the greatest mobility, and act as 
a lubricator to the other minerals. But the mica plates, likewise, would 
probably slip or slide readily over one another when brought by pres- 
sure and friction into parallel planes, and the rectangular crystals of 
felspar would be likely to offer the greatest resistance to the motion, and 
bo therefore broken up in part, and dragged into those layers or stripes 
which are characteristic of the position of this mineral in gneiss. Where 
the pressure and friction was extreme, as towards the outer sides of the 
erupted mass, the felspar might be so comminuted as to be undis- 
tinguishable, or be taken up, perhaps, into the silicate, which, with the 
mica, would then appear to constitute the entire rock, so as to present 
ultimately the structure and composition of Jliea- schist ; while the 
irregularities of friction being equally extreme in the same parts would 
be likely to occasion multiplied wavings and convolutions on the small 
as well as large scale, such as we see in that rock, as well as in 
serpentines and other of the so-called metamorphic schists. 
Further yielding of the mass to pressure, occasioning internal move- 
ments, after more or less of consolidation, or even the mere shrinkage 
during that process, might give rise to cracks and fissures, which, being 
filled by infiltration of the silicate from the proximate parts, woiild 
occasion the quartz veins so frequent in these crystalline schists. 
It is submitted whether such a purely mechanical re-arrangement 
as is here indicated, and which would seem from v, priori reasoning abso- 
lutely a necessary accompaniment of the protrusion of any subterranean 
granitic axis, by internal dilatation from increased temperature, through 
disrupted overlying rocks, docs not oflPera more probable explanation of 
the foliated structure of the (so-called) metamorphic schists than the 
supposition that it is merely the original sedimentary bedding of other- 
wise wholly metamorphosed strata ? It seems difficult to understand 
that exposure to an amount of heat and pressure infinitely greater than 
that which, in the argillaceous schists, has nearly obliterated all traces 
of the original bedding, should in mica-schist and gneiss have ren Icrcd 
it only more distinct and decided. 
That these are, or may be, metamorphic rocks, derived, that ip, from 
