33g
Art of Travel.
another pot buried in the earth. 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.- Turpen tine 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 goat'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. After dressing the hide, two strongish pieces of wood are sewn along the slit, one at each side, just like the ironwork on each side of the mouth of a carpet-bag, and for the same purpose, i.e. to strengthen it : a nozzle is inserted at the neck. To use this apparatus, its mouth is opened, and pulled out ; then it is suddenly shut, by which means the bellows are made to enclose a bagful of air; this, by pushing the mouth flat home, is ejected through
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