at the processes of vegetable life, by absorbing various
gases from the atmosphere, cause so large a mass of solid matter to
accumulate on the surface of the land, that this mass alone may
constitute a great counterpoise to all the matter transported to lower
levels by the aqueous agents of decay. "Torrents and rivers," it is
said--"the waves of the sea and marine currents--act upon lines only;
but the power of vegetation to absorb the elastic and non-elastic fluids
circulating round the earth, extends over the whole surface of the
continents. By the silent but universal action of this great antagonist
power, the spoliation and waste caused by running water on the land,
and by the movements of the ocean, are neutralized, and even
counterbalanced."[995]

In opposition to these views, I conceive that we shall form a juster
estimate of the influence of vegetation, if we consider it as being in a
slight degree conservative, and capable of retarding the waste of land,
but not of acting as an antagonist power. The vegetable mould is seldom
more than a few feet in thickness, and frequently does not exceed a few
inches; and we by no means find that its volume is more considerable on
those parts of our continents which we can prove, by geological data, to
have been elevated at more ancient periods, and where, consequently,
there has been the greatest time for the accumulation of vegetable
matter, produced throughout successive zoological epochs. On the
contrary, these higher and older regions are more frequently denuded, so
as to expose the bare rock to the action of the sun and air.

We find in the torrid zone, where the growth of plants is most rank and
luxurious, that accessions of matter due to their agency are by no means
the most conspicuous. Indeed it is in these latitudes, where the
vegetation is most active, that, for reasons to be explained in the next
chapter, even those superficial peat mosses are unknown which cover a
large area in some parts of our temperate zone. If the operation of
animal and vegetable life could restore to the general surface of the
continents a portion of the elements of those disintegrated rocks of
which such enormous masses are swept down annually into the sea, the
effects would long ere this have constituted one of the most striking
features in the structure and composition of our continents. All the
great steppes and table-lands of the world, where the action of running
water is feeble, wo