part of that wise system of
nature, in which nothing is done in vain, and in which every thing
tends to accomplish the end with the greatest marks of economy and
benevolence. Had it been otherwise, and the demolishing powers of the
land increased, in a growing rate with the diminution of the height,
the changes of this earth and renovation of our continent, in which
occasionally animal life must suffer, would necessarily require to be
often repeated; and, in that case, chaos and confusion would seem to be
introduced into that system which at present appears to be established
with such order and economy that man suspects not any change; it
requires the views of scientific men to perceive that things are not at
present such as they were created; it requires all the observation of a
natural philosopher to know that in this earth there had been change,
although it is not every natural philosopher that observes the
benevolence accompanying this constitution of things which must subsist
in change.]

The slope which our author gives to his mountains, in order to secure
them from the ravages of time, is that which, according to his own
reasoning, renders them fertile and proper for the culture of man; but
fertile soil yields always something to the floods to carry away; and,
while any thing is carried from the soil, the land must waste, although
it may not then waste at the rate of those within the valleys of the
Alps. According to the doctrine of this author, our mountains of
Tweeddale and Tiviotdale, being all covered with vegetation, are arrived
at that period in the course of things when they should be permanent.
But is it really so? Do they never waste? Look at the rivers in a
flood;--if these run clear, this philosopher has reasoned right, and I
have lost my argument. Our clearest streams run muddy in a flood. The
great causes, therefore, for the degradation of mountains never stop as
long as there is water to run; although, as the heights of mountains
diminish, the progress of their diminution may be more and more
retarded.

Let us now see how far our author has reasoned justly with regard to
vegetation, which, he says, stops the effects of all the little causes
of destruction; this is the more necessary, as, in the present theory,
it is the little causes, long continued, which are considered as
bringing about the greatest changes of the earth.

Along the courses of our rivers there are plains between the mountains