60 REPORT—1862. 
could give rise to what have been called “craters of elevation,” “valleys of eleva- 
tion,” or any other large openings of the surface of the ground. I would go even 
further than this, and hesitate to believe that any high inclination or great con- 
tortion had ever been imparted to any beds at, or close to, the surface*. I believe 
all such disturbed positions to have been acquired by a slow creeping movement, 
the result of the combination of great force acting against almost, but not quite, 
equally great superincumbent pressure, and therefore at a correspondingly great 
depth, and that, by the very constitution of the interior of the earth, such great 
force could not be brought to bear upon any mere point or line of the surface. 
The rocks thus disturbed ultimately arrive at the surface, because they have 
been laid bare by the stripping off of veil after veil of covering, by the external 
erosive forces acting over the upraised area—upraised either during the disturbance, 
or by a subsequent action of elevation of a broader and more equable character. 
These same combined actions, still further carried out, ultimately bring to the sur- 
face the Metamorphosed Schists, which had heen deeply buried by the converse 
actions of depression and deposition, as well as the granitic masses, which, pro- 
ceeding from the interior, slowly worked their way upwards to a certain height, 
but cooled and consolidated before they were able to approach the surface as it 
existed at the time of their intrusion. 
No one can study a mountainous district, in which the rocks have been greatly 
bent and broken, with the same care and attention that has been bestowed by the 
Geological Survey on the mountains of the British Islands, without perceiving that 
the external features, whether of hill or valley, do not depend on the frangibility of 
the rocks, but on their relative power of resistance to erosive action. The hard 
siliceous rocks, or those best adapted to resist the chemical and mechanical action 
of water, form the prominences ; the softer or more soluble rocks form the valleys 
and low grounds, ‘The upward or anticlinal curves in the beds, over which, if any- 
where, external gaping fissures would be formed, are at least as often marked 
by the occurrence of hills and ridges over them as of valleys, the external feature 
depending altogether on the ‘ weatherable”’ nature of the rock. 
The same reasoning is applicable to great faults and dislocations. We are all 
familiar with the fact that, of faults that have a dislocation of hundreds or even 
thousands of feet, there is often not the least indication at the surface of the ground, 
which may be a perfect plain, or may undulate, without any regard to the subter- 
ranean structure of the rocks. This seems to me to be strong evidence in favour 
of the supposition that these dislocations never did make any great feature at the 
surface. The amount of dislocation has been gained foot by foot and inch by inch 
below, the movement being so slow as to allow of the surface-irregularity being 
always diminished or obliterated as fast as it was formed. If a great disloca- 
tion had taken place at once, and an equally great cliff had been formed by it, 
surely the traces of such a feature would have been more often preserved than they 
are. 
Small cliffs do occur sometimes along the line of a fault, but only when it so hap- 
pens that at the present surface of the ground a hard unyielding rock is brought 
against a soft and more perishing one ; and the cliff or bank is always in proportion 
to the “weatherable ” natures of the two rocks, and not to the amount of the dislo- 
cation. In like manner, valleys sometimes run along the line of faults, and especially 
of large faults, and there is sometimes a sort of proportion between the magnitude 
of the dislocation and that of the external feature ; but even in these cases the mag- 
nitudes are not of the same kind, the width of the fault being very slight indeed 
as compared with the width of the valley. The coincidence is one of direction 
only, the original fracture having determined the direction of the subsequent 
* The contortions in the Chalk and the glacial Drift described by Sir C. Lyell, from Messrs. 
Forchhammer and Pugaard, as occurring in the Island of Méen in Denmark, show that 
this belief must be somewhat modified, and that local flexures and fractures do sometimes 
take place even at the surface. If so, then some of those apparent in the Alps and other 
recently formed mountain-chains may have also taken place at or near the surface. It is, 
however, demonstrable in all these cases that subsequent denudation has acted upon these 
areas, though the amount of matter removed may not be so great as the expressions in the 
text would imply. 
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