_Tanning_.
The tanner steeps the skin at first in a weak infusion of bark, until it
has acquired a nutmeg brown colour, and then he gradually increases the
strength of the steeping liquors, and after a time he draws the skin
out, and finds that it is converted into leather. A thick piece of hide
requires ten, twelve, or fourteen months, to be converted into good
leather; and when you consider the length of time consumed in the
process, and the great capital necessarily employed, you cannot feel
surprised that various plans should have been proposed to lessen both.
It was proposed to tan with warm instead of cold liquors; and although
the tan appeared to promote the skins in a shorter time, the quality of
the leather was so much injured, that it was soon given up. Then it was
tried to force the tan through the pores of the skin, by employing great
pressure; but this was not found to answer. But you may ask why the
tanner does not put the skins at once into a strong liquor? The reason
is, that the exterior surface of the skin would soon become tanned, and
the central part would remain untanned, which, in a short time, would
begin to rot and decay, and the leather so treated would soon fall to
pieces. The tanner, therefore, judges of the perfection of the tanning
by cutting through the leather; and if he finds it of an uniform brown
colour, without any white streak in the centre, he considers that the
process has been successfully conducted. It would require much time to
describe all the operations of the _tan-yard_, but many of them are
interesting, as regards the chemical agents employed. I might have
mentioned to you, that the mode of preparing the skin for tanning, is
first to soak it in lime-water, by which the hair is easily detached;
but the cuticle and under part of the skin, the cellular substance, are
scraped off after it has been soaked in the lime water. A great variety
of substances have been used for tanning, as the acorn-cup of the
oriental bark; catechu and sumach have been also used; but the oak bark
is most generally used, as furnishing a large quantity of astringent
matter. It is not the business of the chemist to describe the different
kinds of leather, but I may just mention, that the upper leather of
shoes is called _curried_ leather; the leather having been tanned, is
rubbed over with oil before it is dried, and it is then very flexible,
pliable, and durable; but if you take a piece of dry leather, and try to
rub it over with oil or grease, you cannot make it enter the pores of
the leather; the black colour is produced by rubbing it over with a
solution of green vitriol, the sulphate of iron. _Russian_ leather is
tanned in an infusion of birch bark, and is said to be afterwards mixed
with a quantity of birch tar, to give it that odour for which it is
peculiar, which renders it valuable for book-binding, on account of
preventing it from being attacked by insects. _Tawed_ leather, used for
gloves, is made by impregnating the skin with a liquor containing alum
and salt, and afterwards washed in a mixture of yolks of eggs and water;
the saline and animal matters combine, and give it that peculiar
softness, and such leather is afterwards coloured as may be required;
having been rolled over wooden rollers, in which are grooves, it is
called _Morocco_ leather. These are the principal varieties of leather
employed in this country.--_Brande's Lectures--Lancet_.
_Mites_.
An indefatigable naturalist has undertaken the very difficult task
of arranging the family of _acarides_, or mites; he divides them into
sixty-nine genera, the greater part of them new!
_Electro-Attraction of Leaves_.
The results of a French experimentalist have lately led him to conclude
that the leaves, hairs, and thorns of plants tend to maintain in them
the requisite proportion of electricity; and, by drawing off from the
atmosphere what is superabundant, they also act in some measure as
thunder-rods.
_Enormous Whale_.
The skeleton of a whale, 95 feet long by 18 feet high, has lately been
deposited in the Cabinet of Natural History at Ghent. In the opinion of
many naturalists, among whom is M. Cuvier, this fish could not have been
less than 900 or 1,000 years old!
_Fly in Wheat_.
In North America, much damage is done to crops of wheat by the Hessian
fly. The female deposits from one to eight or more eggs upon a single
plant of wheat, between the vagina or sheath of the inner leaf and the
culm nearest the roots; in which situation, with its head towards the
root or first joint, the young larva pass the winter. They eat the stem,
which thus becomes weak, and breaks; but are checked by another insect,
called the destructor, otherwise whole crops of wheat would be
annihilated.
_Spiders_.
A correspondent of London's _Magazine of Natural History_ says, that he
lately amused himself for more than an hour in observing the proceedings
of a little spider, whose bag of eggs had been removed and restored!
_Light of the Sea_.
Its appearance previous to a storm is a very old observation among
sailors. It is, however without foundation, as it is to be seen, more
or less, all the year round in the Carribean sea, where there are no
storms but in the hurricane months. In the hand it has a kind of mucous
feel.--_Mag. Nat. Hist_.
_Woodpeckers_.
A specimen of the _least woodpecker_ was lately shot near Newcastle; and
another has since been heard and seen near Coventry. Its noise resembles
that made by the boring of a large auger through the hardest wood; whence
the country people sometimes call the bird "the pump-borer."--_Ibid_.
_The Tea Shrub_
Has been naturalized in Java with complete success; so that, sooner or
later, the Chinese monopoly will come to an end.
_Floating Island_.
From the earliest times, there are to be found in authors, notices of the
singular geological phenomena of floating islands. Pliny tells us of the
floating islands of the Lago de Bassanello, near Rome; in Loch Lomond, in
Scotland, there is or was a floating island; and in the Lake of Derwent
Water, in Cumberland, such islands appear and disappear at indefinite
periods. Mr. A. Pettingal, jun. has recently described a floating island,
about a mile southwards of Newbury port, 140 poles in length, and 120 in
breadth. It is covered with trees; and in summer, when dry weather is
long continued, it descends to the bottom of the lake.--_American,
Journal of Science_.
_An immense Medusa_.
A species of sea-serpent, was thrown on shore near Bombay, in 1819.
It was about 40 feet long, and must have weighed many tons. A violent
gale of wind threw it high above the reach of ordinary tides; in which
situation it took nine months to rot; during which process travellers
were obliged to change the direction of the road for nearly a quarter of
a mile, to avoid the offensive effluvia. It rotted so completely, that
not a vestige of bone remained.--(_C. Telfair, Esq. to R. Barclay, Esq.
of Bury Hill._)
_Himalaya Mountains_.
Captain Gerard, in exploring these mountains, with a view to measurement,
had ascended to the height of 19,600 feet, being 400 feet higher than
Humboldt had ascended on the Andes. The latter part of Captain Gerard's
ascent, for about two miles, was on an inclined plane of 42°, a nearer
approach to the perpendicular than Humboldt conceived it possible to
climb for any distance together.--_Heber's India_.
_Hippopotamus_.
The head of a Hippopotamus has recently been brought to England, with
all the flesh about it, in a high state of preservation. This amphibious
animal was harpooned while in combat with a crocodile, in a lake in
the interior of Africa. The head measures near four feet long, and
eight feet in circumference; the jaws open two feet wide, and the
cutting-teeth of which it has four in each jaw, are above a foot
long, and four inches in circumference. Its ears are not bigger than
a terrier's, and are much about the same shape. This formidable and
terrific creature, when full-grown, measures about 17 feet long from the
extremity of the snout to the insertion of the tail, above 16 feet in
circumference round the body, and stands above 7 feet high. It runs with
astonishing swiftness for its great bulk, at the bottom of lakes and
rivers, but not with as much ease on land. When excited, it puts forth
its full strength, which is prodigious. "I have seen," says a mariner,
as we find it in Dampier, "one of these animals open its jaws, and
seizing a boat between its teeth, at once bite and sink it to the
bottom. I have seen it on another occasion place itself under one of our
boats, and rising under it, overset it, with six men who were in it, but
who, however, happily received no other injury." At one time it was not
uncommon in the Nile, but now it is no where to be found in that river,
except above the cataracts.
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