tified sandy clay, spreading over the undulating surface of the
denudated sandstone, following all its inequalities, and filling all its
depressions and furrows. But while the Igarape Grande has dug its
channel down to the sea, cutting these formations, as I ascertained, to
a depth of twenty-five fathoms, it has thus opened the way for the
encroachments of the tides, and the ocean is now, in its turn, gaining
upon the land. Were there no other evidence of the action of the tides
in this locality, the steep cut of the Igarape Grande, contrasting with
the gentle slope of the banks near its mouth, wherever they have been,
modified by the invasion of the sea, would enable us to distinguish the
work of the river from that of the ocean, and to prove that the
denudation now going on is due in part to both. But besides this, I was
so fortunate as to discover here unmistakable and perfectly convincing
evidence of the onward movement of the sea. At the mouth of the Igarape
Grande, both at Soure and at Salvaterra, on the southern side of the
Igarape, is a submerged forest. Evidently this forest grew in one of
those marshy lands constantly inundated, for between the stumps is
accumulated the loose, felt-like peat characteristic of such grounds,
and containing about as much mud as vegetable matter. Such a marshy
forest, with the stumps of the trees still standing erect in the peat,
has been laid bare on both sides of the Igarape Grande by the
encroachments of the ocean. That this is the work of the sea is
undeniable, for all the little depressions and indentations of the peat
are filled with sea-sand, and a ridge of tidal sand divides it from the
forest still standing behind. Nor is this all. At Vigia, immediately
opposite to Soure, on the continental side of the Para River, just where
it meets the sea, we have the counterpart of this submerged forest.
Another peat-bog, with the stumps of innumerable trees standing in it,
and encroached upon in the same way by tidal sand, is exposed here also.
No doubt these forests were once all continuous, and stretched across
the whole basin of what is now called the Para River.

Since I have been pursuing this inquiry, I have gathered much
information to the same effect from persons living on the coast. It is
well remembered that, twenty years ago, there existed an island, more
than a mile in width, to the northeast of the entrance of the Bay of
Vigia, which has now entirely disappeared. Farther