We have seen that upraised marine remains occur at intervals, and in some
parts almost continuously, from latitude 45 degrees 35' to 12 degrees S.,
along the shores of the Pacific. This is a distance, in a north and south
line, of 2,075 geographical miles. From Byron's observations, the elevation
has no doubt extended sixty miles further south; and from the similarity in
the form of the country near Lima, it has probably extended many leagues
further north. (I may take this opportunity of stating that in a MS. in the
Geological Society by Mr. Weaver, it is stated that beds of oysters and
other recent shells are found thirty feet above the level of the sea, in
many parts of Tampico, in the Gulf of Mexico.) Along this great line of
coast, besides the organic remains, there are in very many parts, marks of
erosion, caves, ancient beaches, sand-dunes, and successive terraces of
gravel, all above the present level of the sea. From the steepness of the
land on this side of the continent, shells have rarely been found at
greater distances inland than from two to three leagues; but the marks of
sea-action are evident farther from the coast; for instance, in the valley
of Guasco, at a distance of between thirty and forty miles. Judging from
the upraised shells alone, the elevation in Chiloe has been 350 feet, at
Concepcion certainly 625 feet; and by estimation 1,000 feet; at Valparaiso
1,300 feet; at Coquimbo 252 feet; northward of this place, sea-shells have
not, I believe, been found above 300 feet; and at Lima they were falling
into decay (hastened probably by the salt) at 85 feet. Not only has this
amount of elevation taken place within the period of existing Mollusca and
Cirripedes; but their proportional numbers in the neighbouring sea have in
most cases remained the same. Near Lima, however, a small change in this
respect between the living and the upraised was observed: at Coquimbo this
was more evident, all the shells being existing species, but with those
embedded in the uppermost calcareous plain not approximating so closely in
proportional numbers, as do those that lie loose on its surface at the
height of 252 feet, and still less closely than those which are strewed on