the force of running water, in the narrow bed through which it was
obliged to pass; for, being arrived in the lake, the issue of which
is above the level of its bottom, the moving water loses its force in
protruding heavy bodies, which therefore it deposits. Thus the bottom of
the lake would be filled up, before the heavy materials which the river
carries could be made to advance any farther towards the sea.

Reasoning upon these principles, we shall find, that the general
tendency of the operations of water upon the surface of this earth is to
form plains of lakes, and not, contrarily, lakes of plains. For example,
it was not the Rhone that formed the lake of Geneva; for, had the lake
subsisted in its present state, while the Rhone had transported all the
matter which it is demonstrable had passed through that channel from the
Alps, the bed of the lake must have been made a plain through, which the
river would continue to pass, but in a changing channel, as it does in
any other plain. We are therefore led to believe, that the passage of
the Rhone through the lake, in its present state, is not a thing of long
existence, compared with the depredations which time had made by that
river upon the earth above the lake. But how far there are any means for
judging, with regard to the causes of that change which must have taken
place, and produced the present state of things about this lake, can
only be determined by those who have the proper opportunity of examining
that country.

If lakes are not in the natural constitution of the earth, when this is
elevated from the sea into the place of land, they must be formed by
some posterior operation, which may be now considered.

There are in nature, that is, in the natural operations of the globe,
two ways by which a lake may properly be formed in a place where it had
not before existed. One of these is the sliding or overshooting of a
mountain or a rock, which, being undermined by the river, and pressed by
its weight, may give way, and thus close up the defile through which the
river had worn for itself a passage. The other is the operation of an
earthquake, which may either sink a higher ground, or raise a lower, and
thus produce a lake where none had been before. To which, indeed, may be
added a third, the dissolution of saline or soluble earthy substances
which had filled the place.

So many must have been those alterations upon the surface of the earth
which we inhabit, and