TANNING. 
the pores, and dissolving a sort of greasy 
substance contained in them, and then, by 
means of the astringency and guminy resi- 
nous properties of oak bark, to fill and re- 
unite them, so as to give firmness and dura- 
bility to the whole texture. But this theo- 
ry has been controverted by some chemists, 
who suppose that the animal jelly contained 
in the skin is not dissolved, but unites dur- 
ing the process with the astringent prin- 
ciple of the bark, and forms a combination 
insoluble in water. 
The process of tanning varies considera- 
bly, not only in different countries, but 
even in different parts of the same country. 
The following is the method most approved 
and practised in London and its vicinity. 
The leather consists chiefly of three sorts, 
known by the name of butts or backs, 
hides, and skins. Butts are generally tpade 
from tlie stoutest and heaviest ox hides, and 
are managed as follows: After the horns 
are taken off, the hides are laid smooth in 
heaps for one or two days in the summer, 
and for five or six in the winter: they are 
then hung on poles, in a close room called a 
smoke house, in which is kept a smoulder- 
ing fire of wet tan ; this occasions a small 
degree of putrefaction, by which means tire 
hair is easily got off, by spreading the hide 
on a sort of wooden horse' or beam, and 
scraping it with a crooked knife. The hair 
being taken off, the hide is thrown into a 
pit or pool of watea' to cleanse it from the 
dirt, &c. which being done, the hide is again 
spread on the wooden beam, and the 
grease, loose flesh, extraneous filth, &c. 
carefully scrubbed out or taken off; the 
hides are then put into a pit of strong li- 
quor called ooze or wooze, prepared in pits 
called letches or taps kept for the purpose, 
by infusing ground bark in water; this js 
termed colouring : after which they are re- 
moved into another pit called a scowering, 
which consists' of water strongly impreg- 
nated with vitriolic acid, or with a vegeta- 
ble acid prepared from rye or barley. 
This operation (which is called raising,) by 
distending the pores of the hides, occasions 
tliera more readily to imbibe the ooze, the 
effect of which is to astringe and condense 
Ihe fibres, and give firmness to the leather. 
The hides are then taken out of the scower- 
ing, and spread smooth in a pit commonly 
filled with water, .called a binder, with a 
quantity of ground bark strewed between 
each. 
After lying a month or six weeks, they 
are taken up ; and the decayed bark and 
liquor being drawn out of the pit, it is fil el 
again with strong ooze, when they are put 
in as before, with bark between each hide. 
They now lie two or three months, at the 
expiration of which the same operation is 
repeated; they then remaui four or five 
months, when they again undergo the same 
proce.ss ; and after being three months in 
the last pit, are completely tanned, unless 
the hides are so remarkably stout as to 
want an additional pit or layer. 
The whole process requires from eleven 
to eighteen months, and some times two 
years, according to the substance of the 
hide, and discretion of the tanner. When 
taken out of the pit to be dried, they are 
hung on poles; and after being compressed 
by a steel pin, and beat out smooth by 
wooden hammers called beetles, the opera- 
tion is complete ; and when thoroughly dry,' 
they are fit for sale. Butts are chiefly used 
for the soles of stout shoes. The leather 
which goes under the denomination of hides 
is generally made from cow hides, or the 
lighter ox hides, which are thus managed. 
After the horns are taken off, and the hides 
washed, they are put into a pit of water sa- 
turated with lime, where they remain a few 
days, when they are taken out, and the 
hair scraped off on a wooden beam, as be- 
fore described, they are then washed in a 
pit or pool of water, and the loose flesh, 
&c. being taken off, they are removed into 
a pit of weak ooze, where they are taken 
up and put down (which is technically 
termed handling) two or three times a-day 
for the first week: every second or third 
day they are shifted into a pit of fresh 
002P, somewhat stronger than the former ; 
till at the end of a month or six weeks; 
they are put into a strong ooze, in which 
they are handled once or twice a-week 
with fresh bark for two or three months. 
They are then removed into another pit, 
called a layer, in which they are laid 
smooth, with bark ground very fine, strew'ed 
between each hide. After remaining here 
two or three months, they are generally 
taken up, when the ooze is drawn out, and 
the hides put in again with fresh ooze and 
fresh bark ; where after lying two or three 
months more, they are completely tanned, 
except a few veiy stout hides, which may 
require an extra layer : they are then taken 
out, hung on poles, and being hammered 
and snmothed by a steel pin, are,, when dry, 
fit for sale. These hides are called crop 
