and dark tints of brownish-red, brown and olive-green.

Dr. Lindley's communication was illustrated with specimens of
coloring matters yielded by various lichens collected in the
neighbourhood of Edinburgh, &c.

BARKS FOR TANNING.

Let us now take a brief review of the sources from whence tanning
materials may be obtained, which will also enable us to form a fair
estimate of the prospect of future supplies. Only one medal was
awarded, at the Great Exhibition, for tanning substances, viz., to
Messrs. Curtis, Brothers (United Kingdom, No. 126), but honorable
mention was made of the following competitors:--One from Tunis, one
from Van Diemen's Land, one from New Zealand, one from Belgium, one
from the Cape of Good Hope, one from Canada, and one from the United
Kingdom.

The substance from which pure tannin is most frequently obtained for
chemical purposes is nutgalls, for tannin constitutes above 40 per
cent, of their weight. It may be procured also from several other
sources, such as oak, horse chestnut, sumach, and cinchona barks,
catechu, kino, &c.

The basis of the skins of animals is composed of a substance to which
the name of gelatine is given. One of the properties of this substance
is, that when combined with tannin, it forms the compound of tannate
of gelatine, or leather, a substance which is so useful to mankind.
From time immemorial, the substance employed to furnish the tannin to
the hides of animals, in order to convert them into leather, has been
oak bark. But as the purpose for which oaks are grown is their timber,
and not their bark, the supply of oak bark cannot be calculated upon,
and this is, perhaps, one of the causes why tanning as an art is in
such a backward state.

The consumption of tannin required in the leather manufacture may be
estimated from the fact that more than 672,000 cwts. of raw hides were
imported in 1851, besides the hides of the cattle, &c., consumed in
the United Kingdom. On the Continent and in the United States the
consumption of bark for this purpose is also considerable.

The imports of bark for the use of tanners and dyers has amounted
yearly to the very large quantity of 380,674 cwt., besides what we
obtain at home. Oak bark contains usually the largest proportion of
tannin, and according to Davy's experiments eight-and-a-half pounds of
oak bark are equivalent for tanning purposes to two-and-a-quarter of
galls, three of sumach, seven-and-a-half of Leic