the soil; and this soil is necessarily washed away, by the continual
circulation of the water, running from the summits of the mountains
towards the general receptacle of that fluid. The heights of our land
are thus levelled with the shores; our fertile plains are formed from the
ruins of the mountains; and those travelling materials are still pursued
by the moving water, and propelled along the inclined surface of the
earth[1] These moveable materials, delivered into the sea, cannot, for
a long continuance, rest upon the shore; for, by the agitation of the
winds, the tides and currents, every moveable thing is carried
farther and farther along the shelving bottom of the sea, towards the
unfathomable regions of the ocean.

[Note 1: M. de Luc, in his second letter to me, published in the Monthly
Review for 1790, says, "You ought to have proved that both gravel and
sand are carried from our continents to the sea; which, on the contrary,
I shall prove not to be the case." He then endeavours to prove his
assertion, by observing, that, in certain places where there is not
either sufficient declivity in the surface, or force in the running
water, gravel and sand are made to rest, and do not travel to the sea.
This surely is a fact to which I most readily assent; but, on the other
hand, I hope he will acknowledge, that, where there is sufficient
declivity in the surface, or force in the running water, sand, gravel,
and stones, are travelled upon the land, and are thus carried into the
sea--at last. This is all that my theory requires, and this is what I
believe will be admitted, without any farther proof on my part.]

If the vegetable soil is thus constantly removed from the surface of the
land, and if its place is thus to be supplied from the dissolution of
the solid earth, as here represented, we may perceive an end to this
beautiful machine; an end, arising from no error in its constitution as