The effect of the additional force thus brought
into action can be equal only to one atmosphere, but a further
improvement has been made: the vessel containing the hides is,
after exhaustion, filled up with a solution of tan; a small
additional quantity is then injected with a forcing-pump. By
these means any degree of pressure may be given which the
containing vessel is capable of supporting; and it has been found
that, by employing such a method, the thickest hides may be
tanned in six weeks or two months.
48. The same process of injection might be applied to
impregnate timber with tar, or any other substance capable of
preserving it from decay, and if it were not too expensive, the
deal floors of houses might thus be impregnated with alumine or
other substances, which would render them much less liable to be
accidentally set on fire. In some cases it might be useful to
impregnate woods with resins, varnish, or oil; and wood saturated
with oil might, in some instances, be usefully employed in
machinery for giving a constant, but very minute supply of that
fluid to iron or steel, against which it is worked.
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