SCROPE — ON INTERNAL STRUCTURE OF GNEISSIC ROCKS. 3G7 
the fusion and rc-consolidation in a crystalline state of sedimentary 
strata, is a theory not here called in question. My suggestion only 
amounts to this, that their foliation does not represent the original 
sedimentary bedding, but was brought about by the internal friction of 
their ah'eady crystallized particles during protrusion or elevation, under 
circumstances of intense pressure and lateral motion in opposite or 
nearly opposite directions. 
It is not inconsistent with this view to admit that a certain amount 
of crystallization may have accompanied or followed these internal 
movements. For it is known that some freedom of motion is necessary 
to the exercise of the crystallific action, and also that the atomic 
particles must be brought within certain small distances. Now, during 
the internal movements to which I have referred, some of the dis- 
aggregated mineral elements may be brought so close together as to 
cause crystallization to take place. And thus new and even large 
crystals may be formed in the midst of granular or amorphous matter. 
In many of the crystalline schists, as well as in some clinkstone and 
felspar porphyries, we find lengthened crystals whose acicular and 
delicate, but unbroken, form renders it difficult to suppose them to 
have undergone, since their production, any great amount of friction. 
If we suppose these to have crystallized while the mass of which they 
form part was subjected to a certain amount of motion under intense 
pressure, it will be obvious that their major axes should be found (as I 
believe they invariably are) in planes more or less perpendicular to the 
direction of the pressure, and corresponding to that of the movement 
(as indicated by the foliation of the rock), since the mobility necessary 
to the crystallific action will have been freest in that direction. ■ 
I may remark that the influence of internal friction, caused by 
movements under extreme and irregular pressure, must be equally 
operative in the case of rocks of aqueous as in those of igneous origin — 
of shales, limestones, and grits, as well as of granites or trachytes, under 
similar circumstances of imperfect liquidity, irrespective of change of 
temperature. 
There is every reason to believe that many of the sedimentary strata 
were, at the time of their elevation above the levels at which they were 
deposited, in a more or less soft and semi-liquid condition, permeated 
with water, and consequently liable to much internal and irregular 
movement among their solid particles, under the action of the enormous 
