The Sun.
London, England, 1821-09-22 00:00:00

great part of the year, the inhabitants on the
banks of this river. -The•missionaries and natives

ascribe these endemic fevers to the naked rocks
which TorM the cataracts. That rocks of granite

should engender fever is quite a novel idea, and
rather a • strange one; .yet M. de Ihimboldt
thought it worth art ,\inquiry and examination.—
He remarked, in fact, that these rocks are uni-
formly covered with a coat of black plaistc,.•,
smooth, and apparently a metallic substance; and -
that the colouring matter. is entirely on the sur-
face of the stone, and does not soak through it ;
it cannot be owing to the nature of the rock,
for granite being composed of heterogeneous parts,
the black coating would be thicker on certain
parts of the stone than on others, whereas it is,
on the contrary, uniformly spread over it. l t is,
therefore, a decomposition of the water, which
leaves on the rock an oxide of iron and manga-
nese. Our traveller recollected, that at the ca-
taracts of the Nile, in Nubia, and at those of the
Zaire, in Congo, the same observation was made.
The circumstance of a high temperature, and of
a tumultuous movement of the waters against a
cataract, seems therefore necessary to the forma-
tion of this coating, which gives to all rocks the as-
pect of meteoric stones. To what degree can this
black varnish affect the purity of the air ? To
what'degree does it influence the health of the
inhabitants ? It is evident that these are not idle
questions; and perhaps they will become impor-
tant in endiometry, a science still very obscure
and very uncertain.
I• have before mentioned the muskitos and
gnats, and it may be thought in rather a jocose
strain ; but, if these little animals are unremitting
tormentors of the human race, if they are an ob-
stacle to population, if they prevent the Indians
from congregating in the Missions, and if they
cause villages to be deserted, they then bec-ome
objects of serious consideration; besides, why are
these little and formidable flies to he found in my-
riads on the waters of one river, whilst very few
are to be seen on others? Why does one family
of these vampires prefer black waters, and ano-
ther white waters ? for these two colours distin-
guish the rivers of America, and the black, brown,
or white tint is not solely owing to a greater
or less depth, a greater or less clearness, or to
the nature of the plants which grow on its banks.
This is another question which a scientific tra-
veller ought to endeavour to resolve? We are

too much accustomed to attribute importance
only to great things, but the most diminutive
bodies exercise an enormous and deplorable in-
fluence. What shall we think when we are told
that insects much smaller than gnats, and almost
microscopic, destroy with alarming rapidity skins,
papers, and books ; and that in the vast regions
where these little animals reign like despots, no
monument of the sciences or literature can exist

longer than a few years ? What an obstacle to
perfectibility ! the age of science and know-
ledge will never arrive for the Independents, who
shall build a new Tyre and a new Carthage on
the banks of the Oronoco and the Guaviari !
and it is a mite, an atom, which will retain this
people of heroes in a perpetual middle age! the
.elephant and rhinoceros do not possess this power.
Another observation fills a tolerable number
of pages in this volume, and will no doubt form
the subject of another complaint. Our traveller
has observed with astonishment, that the noise
of the cataracts was thrice more intense during
the night, than in all the time the sun was above
the horizon. At London and Paris, this would
be a very natural effect; but in a 'desert where
silence and the trifling noise caused by the mo-
tion of the leaves, and by nocturnal and diurnal
animals are always the same, why is the noise of
the cataracts so different ? Must we seek the
cause of this phenomenon in the difference of
the density of the air, in the motion given to the
atmosphere by the heat of the sun, in the aeri-
form fluids which during the day mingle with
the atmospheric mass, and deaden or dissipate
the sonorous particles ? This discussion, prose-
cuted with uncommon ability, may perhaps ap..
pear long, and I am going to make it still loniser,
Lecause it seems to me that M. de Humboldt
very improperly admitted only physical causes
into his calculation: A moral cause, and a very
evident one, must influence this increase .of the
intensity of sound. When darkness deprives us
of sight, our other senses acquire increased
powers, and make amends for the want of that
which is thus rendered useless ; the sense of
hearing is on the alert, our attention redoubles,
and we perceive the slightest modifications of the
most feeble noises ; the soand seems magnified
because we make use, as it were, only of an auri-
cular microscope ; in short we hear during the
day, but we listen during the night ; and the dif-
ferent actions denoted by these two verbs ac-
counts in a certain degree for an apparent 'dif-
ference in the perception of sounds at the two
periods of time.
M. de Humboldt is not always absorbed in

natural philosophy : the descriptions he gives us'
are frequently savage panoramas, bUt picturesque
and novel. Here, from the summit of a height,
he makes me contemplate this large 'river which
surmounts every obstacle, these torrents of sil-
very vapours which float above those numberless
black rocks, subdued by the Oronoco, and
these gigantic palms, the tops of which rise above
the rocks and the mists. A little farther he
chews me a jaguar, the rival of the tiger in fero-
city, who has just frisked into a field where two
children are lying on the grass ; he conies close
to them, by taking a few leaps which have no-
thing terrifying in them ; he gives a few pats of
the paw to one of the children, and he runs away,
continuing his gambols, as soon as the little girl,
armed with a branch of a tree, has punished him