204 
POPULAR SCIENCE REVIEW. 
the large scale^ this method of representation gives a correct 
idea of the relations which the strata bear to each other, 
practically their original horizontal position has in most cases 
been so disturbed by the projection through them of those 
masses of igneous rock, of which the backbone of the earth^s 
hills and mountains is composed, that the surface of the gi’ound 
itself and the strata beneath it have been tilted up and con- 
torted in every possible direction. A very little consideration 
will show that such an arrangement as this is eminently 
favourable, not only to the drainage of the surface of the land 
from those accumulations of water with which heavy and 
continuous rains would otherwise soon cover it, but also to 
that system of subterranean drainage by which the water that 
sinks below the surface is collected into a series of channels, 
by which it is conducted into its great reservoir — the ocean. 
But this irregularity of stratification serves other ends than 
the mere facilitation of drainage. From the tendency which 
all strata have, in consequence of their occasional angular 
elevation, to crop out,^^ as it is technically called, at difierent 
portions of the eartlFs surface, the rain which falls upon the 
ground has an opportunity of penetrating those dee]3er strata 
which would otherwise be protected by the impermeable ones 
that lie above them ; and thus all the more soluble portions of 
the earth^s crust are, to a great extent, wasted alike, and each 
contributes its share to those new beds of sediment, which 
now, as in times past, are continually forming beneath the 
waters of the ocean. 
But now let us suppose that instead of this state of things 
the various strata had been undisturbed in then* primitive 
arrangement, and had continued horizontal in their position 
throughout ; that the surface of the earth was unbroken by 
mountains or valleys ; and that its seas and lakes were merely 
excavations in it, like so many holes cut into a pile of thin 
bread-a;nd-b utter. What would have been the result in a 
hydrographical point of view ? Amongst other things it is 
very clear that the rain which fell on the ground would have 
had to remain there until it soaked away downward instead of 
running off into a series of definite channels as it does now on 
all surfaces that are at all inclined. Having, however, made 
its way down for a certain distance through the porous coating 
of mould, sand, gravel, &c., which forms the superficial covering 
of the earth in most parts, it wmald, ere long, have been 
arrested in its course by the first impervious stratum at which 
it arrived, and there it would have accumulated until it acquired 
sufficient pressure to ooze out in all directions into the sea. 
There would have been no rivers, for there would have been 
neither the physical elevations nor the conditions of unequal 
