"THE VOYAGE OF THE BEAGLE" - читать интересную книгу автора (Darwin Charles)

from the insects is so loud, that it may be heard even in a
vessel anchored several hundred yards from the shore; yet
within the recesses of the forest a universal silence appears
to reign. To a person fond of natural history, such a day
as this brings with it a deeper pleasure than he can ever hope
to experience again. After wandering about for some hours,
I returned to the landing-place; but, before reaching it, I
was overtaken by a tropical storm. I tried to find shelter
under a tree, which was so thick that it would never have
been penetrated by common English rain; but here, in a
couple of minutes, a little torrent flowed down the trunk.
It is to this violence of the rain that we must attribute the
verdure at the bottom of the thickest woods: if the showers
were like those of a colder climate, the greater part would
be absorbed or evaporated before it reached the ground. I
will not at present attempt to describe the gaudy scenery
of this noble bay, because, in our homeward voyage, we
called here a second time, and I shall then have occasion to
remark on it.

Along the whole coast of Brazil, for a length of at least
2000 miles, and certainly for a considerable space inland,
wherever solid rock occurs, it belongs to a granitic formation.
The circumstance of this enormous area being constituted of
materials which most geologists believe to have
been crystallized when heated under pressure, gives rise to
many curious reflections. Was this effect produced beneath
the depths of a profound ocean? or did a covering of strata
formerly extend over it, which has since been removed?
Can we believe that any power, acting for a time short of
infinity, could have denuded the granite over so many thousand
square leagues?

On a point not far from the city, where a rivulet entered
the sea, I observed a fact connected with a subject discussed
by Humboldt. [7] At the cataracts of the great rivers
Orinoco, Nile, and Congo, the syenitic rocks are coated by
a black substance, appearing as if they had been polished
with plumbago. The layer is of extreme thinness; and on
analysis by Berzelius it was found to consist of the oxides
of manganese and iron. In the Orinoco it occurs on the
rocks periodically washed by the floods, and in those parts
alone where the stream is rapid; or, as the Indians say, "the
rocks are black where the waters are white." Here the coating
is of a rich brown instead of a black colour, and seems
to be composed of ferruginous matter alone. Hand specimens
fail to give a just idea of these brown burnished stones
which glitter in the sun's rays. They occur only within the
limits of the tidal waves; and as the rivulet slowly trickles
down, the surf must supply the polishing power of the cataracts