land which declines on every side, an enormous mass of travelled soil
appears; or why in other places, where the immediate cause is equally
unseen, the solid strata should be exposed almost naked to our view. We
know the agents which nature has employed for those purposes; we know
the operations in which the solid parts are rendered soil of various
qualities and for different purposes; and when we find the marks of
those natural operations in places where, according to the present
circumstances, the proper agents could not have acted or existed, we are
hereby constrained to believe, that the circumstances of those places
have been changed, while the operations of nature are the same.

It is thus that we shall find reason to conclude an immense period of
time, in those operations which are measured by the depradations of
water acting upon the surface of the earth; a period however which is to
be esteemed a little thing compared with that in which a continent had
taken birth and gone into decay; but a period which interests us the
more to examine, in that it approaches nearer to another period, for the
estimation of which _some data_ may perhaps be found by naturalists and
antiquaries, when their researches shall be turned to this subject. It
is only in this manner that there is any reasonable prospect of forming
some sort of calculation concerning that elapsed time in which the
present earth was formed, a thing which from our present data we have
considered as indefinite.

In this view which we are now taking of the surface of the earth,
nothing is more interesting than the beds of rivers; these take winding
courses around the hills which they cannot surmount; sometimes again
they break through the barrier of rocks opposed to their current; thus
making gaps in places by wearing away the solid rock over which they
formerly had run upon a higher level; and thus leaving traces of their