Public ledger. [volume] (Memphis, Tenn.) 1865-1893, 1866-11-08
AGASSIZ ON BRAZIL.

to lecture delivered by Prof Agassiz
on the valley of the Amazon. The same
distinguished lecturer, who now,lsince the
death of Humboldt, may be considered
as the first naturalist in the world, has
commenced course of twelve lectures
on the results of his expedition to Brazil.
The first of these was given on Tuesday
evening to crowded and scientific au-
dience. The great object which he had
proposed in this expedition, and which
was pre-arranged with his sixteen as
sistants, was to ascertain the geographi
cal distribution of organized beings In
Brazil. AS to the question of when they
began to exist, he said How can we
settle the when until we have ascertained
the iohere7" Owing to the vast extent
of this country, all information on these
points in regard to Brazil has been very
loose. For many reasons, such as the
rowing nature of land animals, he con-
sidered the distribution of aquatic ami
mails (6sh) the most important, and their
natural localities the great matter to be
settled first
His assistants had all worked indus
triously and zealously in conformity to
his plan One young man, Mr.. Thomas
Ward, had explored the head waters of
the Parana, the Araguay and the Zingeu
rivers, at great personal risk, travelling
through the interior table land away
from civilization, among untamed In
dians, descending one of the tributaries
in canoe, and joining him on the Am
azon after an absence Of seven months.
Three others also explored parts OF the
same regions, especially for specimens
of their birds. Agassiz, with several Of
his assistants, took the Amazon from
west to cast. running as it does for $500
miles almost parallel to the equator, 5000
of which he had examined,
Two great facts impressed themselves
upon his notice The fishes of the larger
water basins were quite different from
those of the smaller, and the fishes Of
the head paters quite distinct from
those of the mouths of the rivers. In
Europe. he had noticed in Switzerland
that the fishes of the rivers of the head
waters of the Danube, Of the Rhone and
of the Rhine, where they came into the
same region, were alike, though those at
their mouths were quite distinct In
Brazil, the upper waters OF several
rivers come close together, as from diff
ferent sides of the same range of noun
toins-like those of the Parana or Par.
anabyba. and of the San Francisco and
of the Tocantins; but up to the present
he has had no time to examine and com.
pare the specimens of fishes preserved
hv his different assistants on these diff
ferent streams sufficiently to state the
result.
With regard now to the Amazon, the
first question TO be settled was whether
the fishes were migratory like the salmon
which leaves the fresh waters for propa-
eating, but returns to the sea at other
times The facilities afforded him by
the Brazilian Government, especially the
orders sent to the Governors and other
afficers, had enabled him to make stimuli
toneous collections over vast extent OF
waters, and he was also able, six months
later, to re-examine the same waters,
and others, to determine that the fishes
did nof emigrate, but we're stationary.
There are, perhaps, few exceptions, yet
very few. The tide rises and falls twelve
to fifteen feet regularly for a considerable
distance inland; otherwise, and beyond
that, the waters are sluggish, and ilow
over vast marshes and among inumerable
islands.
There was a time when the land at the
mouth of the Amazon extended hundreds
of miles into what is now the sea, and to
This moment, instead of forming delta,
as most rivers do from the mud they de-
nosit the solid land is being all the time
swept away by the encroachments, con-
stantly going on, of the Atlantic ocean.
From Cape st. Rogue current sweeps
mn northwest along tho shore, and not
only carries away all the deposit of the
river, but the shore line. The river Para
originally flowed into the Atlantic only
"a a part of the Amazon, OF which 1t was
properly q tributary. This eneroach-
ment on the land is now yearly sweeping
away government works, lighthouses,
and even private houses, which, when
built, stood far inland. The whole val
lev Of the Para is to be considered,
therefore, as part Of the valley OF the
Amazon. :,
In this valley the same rocks extend
right across the continent, from the foot
of the Andes to the Atlantic, $500 miles.
These rocks are three in number. The
lowest, which is just exposed at the low.
est stage Of the waters, is a lsminated
clay, the layers being very thin and so
uniform in the hight TO which they rise
as TO form 3 perfect water level, also
provine that the river basin has not
Changed its level since that clay was de-
posited. Above this is sandstone,
Containing more or less Of iron. Hum