the leather of the substances used in its production. That is why we
have made the completest possible analysis of different leathers.

Besides ordinary oak bark there are used at present very different
substances, such as laurel, chestnut, hemlock, quebracho and pine bark,
sumac, etc.

Water is an element that exists in all hides, and it is necessary to
take it into consideration in the analysis. It is present in perceptible
quantity even in dry hides. This water cannot be entirely eradicated
without injuring the leather, which will lose in suppleness and
appearance. Water should then be considered as one of the elements of
leather, but it must be understood that if it exceeds certain limits,
say 12 to 14 per cent., it becomes useless and even injurious. Moreover,
if there is any excess over the normal quantity, it becomes deceptive
and dishonest, as in such a case one sells for hides that which is
nothing but water. Supposing that a hide, instead of only 14 per cent.,
contained 18 per cent. of water, it is evident that in buying 100 pounds
of such a hide one would pay for four pounds of water at the rate for
which he purchased the hide.

There are, also, some matters soluble in air, which are formed to a
large extent from fat arising as much from the hide as from tanning
substances. The air dissolves at the same time a certain amount of
organic acid and resinous products which the hide has absorbed. After
treating with air, alcohol is used, which dissolves principally the
coloring matters, tannin which has not become assimilated, bodies
analogous to resin, and some extractive substances.

That which remains after these methods have been pursued ought to be