small sudden starts, or quite gradual; in this latter case the unrolled
shells having been thrown up during gales beyond the reach of the waves
which afterwards broke on the slowly emerging land. I have made these
remarks, chiefly because I was at first surprised at the complete
difference in nature, between this broad, smooth, upraised bed of shells,
and the present shingle-beach at the foot of the low sandstone-cliffs; but
a beach formed, when the sea is cutting into the land, as is shown now to
be the case by the low bare sandstone-cliffs, ought not to be compared with
a beach accumulated on a gently inclined rocky surface, at a period when
the sea (probably owing to the elevatory movement in process) was not able
to eat into the land. With respect to the mass of nearly angular, salt-
cemented fragments of sandstone, which lie under the shells, and which are
so unlike the materials of an ordinary sea-beach; I think it probable after
having seen the remarkable effects of the earthquake of 1835 (I have
described this in my "Journal of Researches" page 303 2nd edition.), in
absolutely shattering as if by gunpowder the SURFACE of the primary rocks
near Concepcion, that a smooth bare surface of stone was left by the sea
covered by the shelly mass, and that afterwards when upraised, it was
superficially shattered by the severe shocks so often experienced here.

The very low land surrounding the town of Callao, is to the south joined by
an obscure escarpment to a higher plain (south of Bella Vista), which
stretches along the coast for a length of about eight miles. This plain
appears to the eye quite level; but the sea-cliffs show that its height
varies (as far as I could estimate) from seventy to one hundred and twenty
feet. It is composed of thin, sometimes waving, beds of clay, often of
bright red and yellow colours, of layers of impure sand, and in one part
with a great stratified mass of granitic pebbles. These beds are capped by
a remarkable mass, varying from two to six feet in thickness, of reddish
loam or mud, containing many scattered and broken fragments of recent