EUCALYPTUS TREES. 459 
that the perfectly- dried bark contains about 25 per 
cent. of mimosa tannin. The aqueous infusion of the 
bark can be reduced, by boiling, to a dry extract, 
Which, in medicinal and other respects, is equal to 
the best Indian catechu, as derived from Acacia cat- 
echu and A. sundra. It yields, approximately, 80 per 
cent., about half of which, or more, is mimosa tannic 
acid. This catechu is also of great use for preserving © 
against decay articles subject to exposure in water, 
such as nets, fishing-lines, ete. While, according to 
Mr. Simmons, the import of the bark of oaks and 
hemlock-spruce into England becomes every year les~, 
and, while the import of sumach and gambir does not 
increase, the annual demand has, since the last 20 
years, become doubled. Probably no other tanning- 
plants give so quick a return in cultivation as our 
Acacia pycnantha, and particularly A. decurrens. To 
the latter the Black Wattle is already alluded in the 
list of timber-trees ; but the following additional notes 
may further show the importance of this neglected 
tree. The English price of the bark ranges generally 
from £8 to £11. It varies, so far as experiments un- 
der my direction have shown, in its contents of tan- 
nin, from 18 to 33 per cent. In the mercantile ‘bark 
the percentage is somewhat less, according to the 
state of its dryness — it retaining about 10 per cent. 
moisture. Any bare, barren, unutilized places might 
here be sown most remuneratively with the seeds of 
this Wattle Acacia, to secure a regular and continu- 
ous supply of the bark, which necessarily must fall off 
under the indiscriminate arrangements of obtaining the 
bark from the natural localities of growth. The return 
would be within very few years. One and one half 
