and of denudation in the action of the sea. These are plainest at Chiloe,
where, in a height of about five hundred feet, there are three
escarpments,--at Coquimbo, where in a height of 364 feet, there are five,--
at Guasco, where there are six, of which five may perhaps correspond with
those at Coquimbo, but if so, the subsequent and intervening elevatory
movements have been here much more energetic,--at Lima, where, in a height
of about 250 feet there are three terraces, and others, as it is asserted,
at considerably greater heights. The almost entire absence of ancient marks
of sea-action at defined levels along considerable spaces of coast, as near
Valparaiso and Concepcion, is highly instructive, for as it is improbable
that the elevation at these places alone should have been continuous, we
must attribute the absence of such marks to the nature and form of the
coast-rocks. Seeing over how many hundred miles of the coast of Patagonia,
and on how many places on the shores of the Pacific, the elevatory process
has been interrupted by periods of comparative rest, we may conclude,
conjointly with the evidence drawn from other quarters of the world, that
the elevation of the land is generally an intermittent action. From the
quantity of matter removed in the formation of the escarpments, especially
of those of Patagonia, it appears that the periods of rest in the movement,
and of denudation of the land, have generally been very long. In Patagonia,
we have seen that the elevation has been equable, and the periods of
denudation synchronous over very wide spaces of coast; on the shores of the
Pacific, owing to the terraces chiefly occurring in the valleys, we have
not equal means of judging on this point; and the very different heights of
the upraised shells at Coquimbo, Valparaiso, and Concepcion seem directly
opposed to such a conclusion.

Whether on this side of the continent the elevation, between the periods of
comparative rest when the escarpments were formed, has been by small sudden
starts, such as those accompanying recent earthquakes, or, as is most