The Weekly Perrysburg journal. [volume] (Perrysburg, O. [Ohio]) 1861-1???, 1867-04-05
selrtted Mistellang.
From the Scientific Americana
Tho South American Mediter-
ranean.


Professor Agassiz, in his second lecture
FEB. ll) forgot or deferred the sequel OF
the interesting geological history of the con.
tineut AMI devoted the evening to the history
of his expedition and the present terraque,
ous topography of the valley, wit both OF
whichour readers are somewhat acquainted.
Certain points however, struck us with
significance not brought out in former re
ports, and We shall therefore take occasion
to review the ground in a few words.
The valley of the Amazon is no valley to
the eye it's bounds are too distant to be
visible at any point in more than one di-
rection if at all, and it's slopes are altogether
mappreciable by the senses. Even the cur.
rent Of its waters is imperceptible, and
sometimes locally reversed ; so that it pre-.
seuts to the vOyager no other appearance
than that of an inland sea with a long low
distant shore. On either side, the tributa-
res have a similar appearance; they are
thems elves so enormous that the eye can
not span their breadth for example, there
are four rivers descending from the Gnia-
mas on the north, east of the Rio Negro,
hardly noticed on our common maps by
name, yet of a wonderlut size, ono of them
being no less than thirty miles vide at the
mouth. Not to speak of the great affiuents
the Xingu presents at its junction with the
main river front of forty miles broad, and
TIE Tocantins, of sixty ; aud of all them it
must be remembered that you ascend from
the junction from a hundred and fifty to
hundreds Of miles before any appearance Of
rocks or minerals cali be found. The front
OF the united rivers, with their nearly
oceanic depth, at ore of their final outlets,
is 100 miles across, and its yelowish white
hne Qike coffee and milky tinges the ocean
far out of sight OF land.
Nor is the Amazon, when you imagine
its to the eye Rhoreless breadth 10 be con-
ceived as simple stream or belt Of water.
1t is a system. prevailing the country with
unuumhered channels and branches for hun
dreds OF miles in breadth. independently
of the usual Instructions and partings Of
streams, this system has structure pecu.
liar to itself, resulting from remarkable
causes. Tho swelling of the water will
amount TO from thirty to fifty feet, every
rainy season, and the remarkable fact is
! that this takes place from two opposite
quarters, the North and the South, not at
the same time, but alternately.
The SHOWS Of the Andes melt in August
and September, and reach the Amazon by
! October or November. The rains also be-
gin OH the south side in September, and
! the swelling of the southern tributaries
pours into the great bed about the last Of
! November. Both inundatons continue
with increasing volume until March, when
| tie entire sea rises sometimes at the rate
! of a loot in twenty-fOur hours. At the
same time the tributary rivers from the
north are at their lowest stage and bearing
| in mind the fact that the fall of their chan.
nels Tor a long distance hardly exceeds that
| Of the Amazon, or ten feet in "A hundred
| M les tits evident that rise of thirty TO
| fifty feet in the main river must not only
send vast backwater up the northern trib.
ntaries for hundreds of miles. but must fol.
low The dtpressions of the ground in every
direction, aud create network of innu.
merab,o water courses.
Atthe hight of the southern freshet in
March the rains begin on the north, As
the southern rivers suOside, the northern
rivers swell. and come down in full food
about June, TO gorge in turn tne channels OF
their southern rivals, and TO press the swol-
len tide up the southern side of its basin
in the summer, as it rose upon the north
ern side in winter. Thus the water sys'
TEN we are describing resembles an ocean
not only in extent and evenness of surface,
but also in its (semi-annuaD tides.
The result is that all the roads in this
wonderful country are ready made They
are water reads, or ship canals on the
grandest scale of nature. through which
tho united nayies OF the world might steam
or sail in company, for 1000 miles from
east to west and 800 miles on each side
on 900 miles from north to south freely
penetrating every portion of the country
through the profusion of cross eotrses by
which the rivers, swollen on both sides as
we have SEEN twice year. have over