what takes place constantly among hills,--that the
river, as it passes through the valley, will fall backwards and forwards
from side to side, lying first, if I may so speak, with all its weight
against the hills on the one side, and then against those on the other;
so that, as here it is exquisitely told, in each of its circular sweeps
the whole force of its current is brought deep and close to the bases of
the hills, while the water on the side next the plain is shallow,
deepening gradually. In consequence of this, the hills are cut away at
their bases by the current, so that their slopes are interrupted by
precipices mouldering to the water. Observe first, how nobly Turner has
given us the perfect unity of the whole mass of hill, making us
understand that every ravine in it has been cut gradually by streams.
The first eminence, beyond the city, is not disjointed from, or
independent of, the one succeeding, but evidently part of the same
whole, originally united, separated only by the action of the stream
between. The association of the second and third is still more clearly
told, for we see that there has been a little longitudinal valley
running along the brow of their former united mass, which, after the
ravine had been cut between, formed the two jags which Turner has given
us at the same point in each of their curves. This great triple group
has, however, been originally distinct from those beyond it; for we see
that these latter are only the termination of the enormous even slope,
which appears again on the extreme right, having been interrupted by the
rise of the near hills. Observe how the descent of the whole series is
kept gentle and subdued, never suffered to become steep except where it
has been cut away by the river, the sudden precipice caused by which is
exquisitely marked in the last two promontories, where they are defined
against the bright horizon; and, finally, observe how, in the ascent of
the nearest eminence beyond the city, without one cast shadow or any
division of distances, every yard of surface is felt to be retiring by
the mere painting of its details,--how we are permitted to walk up it,
and along its top, and are carried, before we are half way up, a league
or two forward into the picture. The difficulty of doing this, however,
can scarcely be appreciated except by an artist.

Sec. 21. The use of considering geological truths.

I do not mean to assert that this great painter is acquain