evidence
rest solely on geological facts, though doubtless they furnish much
important data. History must aid the inquiry. Tradition and the
recollections of old persons must be attended to. According to these
authorities, a change more or less considerable has taken place in the
level of the coast, after every great earthquake. If we refer to the
account given by Ulloa, and compare the plan of the harbor of Callao,
drawn by him in 1742, with the most correct modern charts, we do not
find much difference in the representations of the distance between
the main-land and San Lorenzo. Four years afterwards the great
earthquake occurred, which destroyed the city of Callao, and plunged
it into the sea. Subsequently there was a rising of the coast, which
could not be inconsiderable, for according to the statements of old
inhabitants of Callao, the distance from the coast to San Lorenzo was
so inconsiderable that boys used to throw stones over to the island.
At present the distance is nearly two English miles. I have no doubt
of the general correctness of those statements, for a careful
investigation of facts leads to the same conclusion; so that within
the last sixty or seventy years the sinking must have been
considerable. It must be observed, however, that the ruins on the
small tongue of land are not, as Darwin supposes, the remains of the
city of Callao, swallowed up by the sea in 1746, but of the Callao
which was destroyed by the great earthquake of 1630.

Another proof of the sinking exists in the extensive shallow between
the coast of the main-land and San Lorenzo, called the Camotal. In
early times this shallow was dry land, producing vegetables, in
particular _Camotes_ (sweet potatoes), whence the name of this portion
of the strait is derived. The inundation took place in the time of the
Spaniards, but before 1746, either in the great earthquake of 1687, or
in that of 1630.

Northward of the Bay of Callao, near the plantation of Boca Negra, there
is a shallow, where, according to records, there existed a sugar
plantation about fifty years ago. Turning to the south of Callao, in the
direction of Lurin, we find, at the distance of about two English miles
from the coast, two islands or rocks, of which one is called Pachacamac,
and the other Santa Domingo. At the time of the Spanish invasion these
rocks were connected with the main-land, and formed a promontory. On one
of them stood a temple or castle. At what period t