The narrow coast-plain sends, as before stated, an arm, or more correctly a
fringe, on both sides, but chiefly on the southern side, several miles up
the valley. These fringes are worn into steps or terraces, which present a
most remarkable appearance, and have been compared (though not very
correctly) by Captain Basil Hall, to the parallel roads of Glen Roy in
Scotland: their origin has been ably discussed by Mr. Lyell. ("Principles
of Geology" 1st edition volume 3 page 131.) The first section which I will
give (Figure 9), is not drawn across the valley, but in an east and west
line at its mouth, where the step-formed terraces debouch and present their
very gently inclined surfaces towards the Pacific.

The bottom plain (A) is about a mile in width, and rises quite insensibly
from the beach to a height of twenty-five feet at the foot of the next
plain; it is sandy, and abundantly strewed with shells.

Plain or terrace B is of small extent, and is almost concealed by the
houses of the town, as is likewise the escarpment of terrace C. On both
sides of a ravine, two miles south of the town, there are two little
terraces, one above the other, evidently corresponding with B and C; and on
them marine remains of the species already enumerated were plentiful.
Terrace E is very narrow, but quite distinct and level; a little southward
of the town there were traces of a terrace D intermediate between E and C.
Terrace F is part of the fringe-like plain, which stretches for the eleven
miles along the coast; it is here composed of shingle, and is 100 feet
higher than where composed of calcareous matter. This greater height is
obviously due to the quantity of shingle, which at some former period has
been brought down the great valley of Coquimbo.

Considering the many shells strewed over the terraces A, B, and C, and a
few miles southward on the calcareous plain, which is continuously united