Make all air-tight with wet clay round the upper pot and board,
covering the board, but exposing the bottom of the reversed pot. Make a
grand fire above and round the latter, and the tar will freely drop. It
will be thin and not very pure tar, but clean, and it will thicken on
exposure to the air.
Pitch is tar boiled down.
Turpentine and Resin.--Turpentine is the juice secreted by the pine, fir,
or larch tree, in blisters under the bark; the trees are tapped for the
purpose of obtaining it. Resin is turpentine boiled down.
METALS.
Fuel for Forge.--Dry fuel gives out far more heat than that which is
damp. As a comparison of the heating powers of different sorts of fuel,
it may be reckoned that 1 lb. of dry charcoal will raise 73 lbs. of water
from freezing to boiling; 1 lb. of pit coal, about 60 lbs.; and 1 lb. of
peat, about 30 lbs. Some kinds of manure-fuel give intense heat, and are
excellent for blacksmith's purposes: that of goats and sheep is the best;
camels' dung is next best, but is not nearly so good; then that of oxen:
the dung of horses is of little use, except as tinder in lighting a fire.
Bellows.--It is of no use attempting to do blacksmith's work, if you have
not a pair of bellows. These can be made of a single goat-skin, of
sufficient power, in skilful hands, to raise small bars of iron to a
welding heat. The boat's head is cut off close under the chin, his legs
at the knee-joint, and a slit is made between the hind legs, through
which the carcase is entirely extracted.
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