t this part of Peru has risen eighty-five feet since it
has had human inhabitants. On the north-eastern declivity of San
Lorenzo, which is divided into three indistinctly marked terraces, there
are numbers of shells of those same species of conchyliae which are at
the present time found living on the coast. On an accurate examination
of these shells, Mr. Darwin found many of them deeply corroded. "They
have," he says, "a much older and more decayed appearance than those at
the height of 500 or 600 feet on the coast of Chile. These shells are
associated with much common salt, a little sulphate of lime (both
probably left by the evaporation of the spray, as the land slowly rose),
together with sulphate of soda, and muriate of lime. The rest are
fragments of the underlying sand-stone, and are covered by a few inches
thick of detritus. The shells higher up on this terrace could be traced
scaling off in flakes, and falling into an impalpable powder; and on an
upper terrace, at the height of 170 feet, and likewise at some
considerably higher points, I found a layer of saline powder, of exactly
similar appearance, and lying in the same relative position. I have no
doubt that the upper layer originally existed on a bed of shells, like
that on the eighty-five feet ledge, but it does not now contain even a
trace of organic structure."[2] Mr. Darwin adds, that on the terrace,
which is eighty-five feet above the sea, he found embedded amidst the
shells and much sea-drifted rubbish, some bits of cotton thread, plaited
rush, and the head of a stalk of Indian corn.

San Lorenzo does not appear to have been inhabited in very early ages.
The fragments of human industry which have been found mixed in the
shells have probably been brought thither by fishermen who visit the
island, and often pass the night on it.

Darwin further remarks:--"It has been stated that the land subsided
during this memorable shock (in 1746): I could not discover any proof
of this; yet it seems far from improbable, for the form of the coast
must certainly have undergone some change since the foundation of the
old town," &c.--"On the island of San Lorenzo there are very
satisfactory proofs of elevation within a recent period; this, of
course, is not opposed to the belief of a small sinking of the ground
having subsequently taken place."

But satisfactory evidence of the sinking of the coast is not to be
obtained in a visit of a few weeks' duration; nor must that