Part 30 (1/2)
TIMBER.
Green Wood.--To season Wood.--Green wood cannot be employed in carpentry, as it is very weak; it also warps, cracks, and becomes rotten: wood dried with too great a heat loses its toughness as well as its pliability: it becomes hard and brittle. Green wood is seasoned by was.h.i.+ng out the sap, and then drying it thoroughly. The traveller's way of doing this by one rapid operation, is to dig a long trench and make a roaring fire in it; when the ground is burning hot, sweep the ashes away, deluge the trench with boiling water; and in the middle of the clouds of steam that arise, throw in the log of wood, shovel hot earth over it, and leave it to steam and bake. A log thick enough to make an axletree may thus be somewhat seasoned in a single night. The log would be seasoned more thoroughly if it were saturated with boiling water before putting it into the trench; that can be done by laying it in a deep narrow puddle, and shovelling hot stones into the water. All crowbars, wagon-lifters, etc., should be roughly seasoned as green wood is far too weak for such uses. The regular way of seasoning is to leave the timber to soak for a long time in water, that the juices may be washed out. Fresh water is better for this purpose than salt; but a mineral spring, if it is warm is better than cold fresh water. Parties travelling with a wagon ought to fell a little timber on their outward journey, and leave it to season against their return, in readiness to replace strained axletrees, broken poles, and the like. They might, at all events, cut a ring round through the bark and sap-wood of the tree, and leave it to discharge its juices, die, and become half-seasoned as it stands.
To bend Wood.--If it is wished to bend a rod of wood, or to straighten it if originally crooked, it must be steamed, or at least be submitted to hot water. Thus a rod of green wood may be pa.s.sed through the ashes of a smouldering fire and, when hot, bent and shaped with the hand; but if the wood be dry it must first be thoroughly soaked in a pond or puddle. If the puddle is made to boil by shovelling in hot stones, as described in the last paragraph, the stick will bend more easily. the long straight spears of savages are often made of exceedingly crooked sticks, straightened in the ashes of their camp fires. A thick piece of wood may be well swabbed with hot water, forcibly bent, as far as can be safely done, tied in position and steamed, as if for the purpose of seasoning (see last paragraph), in a trench; after a quarter of an hour it must be taken out, damped afresh if necessary, bent further, and again returned to steam--the process being repeated till the wood has attained the shape required; it should then be left in the trench to season thoroughly. The heads of dog-sledges, and the pieces of wood used for the outsides of snow-shoes, are all bent by this process.
Carpenters' Tools.--Tools of too hard steel should not be taken on a journey; they splinter against the dense wood of tropical countries, and they are very troublesome to sharpen. The remedy for over-hardness is to heat them red-hot; retempering them by quenching in grease. A small iron axe, with a file to sharpen it, and a few awls, are (if nothing else can be taken) a very useful outfit.
As much carpentry as a traveller is likely to want can be effected by means of a small axe with a hammer-head, a very small single-handed adze, a mortise-chisel, a strong gouge, a couple of medium-sized gimlets, a few awls, a small Turkey-hone, and a whetstone. If a saw be taken, it should be of a sort intended for green wood. In addition to these, a small tin box full of tools, all of which fit into a single handle, is very valuable; many travellers have found them extremely convenient. There is a tool-shop near the bottom of the Haymarket and another in the Strand near the Lowthier Arcade, where they can be bought; probably also at Holtzapfel's in Trafalgar Square. The box that contains them is about six inches long by four broad and one deep; the cost is from 20s. to 30s.
Lastly, a saw for metals, a few drills, and small files, may be added with advantage. It is advisable to see that the tools are ground and set before starting. A small ”hard chisel” of the best steel, three inches long, a quarter of an inch wide, and three-eighths thick--which any blacksmith can make--will cut iron, will chisel marks on rocks, and be useful in numerous emergencies.
Sharpening Tools.--A man will get through most work with his tools, if he stops from time to time to sharpen them up. The son of Sirach says, speaking of a carpenter--”If the iron be blunt, and he do not whet the edge, then must he put to more strength; but wisdom is profitable to direct.”--Ecclesiasticus. A small fine file is very effectual in giving an edge to tools of soft steel. It is a common error to suppose that the best edge is given by grinding the sides of the tool until they meet at an exceedingly acute angle. Such an edge would have no strength, and would chip or bend directly. The proper way of sharpening a tool, is to grind it until it is sufficiently thin, and then to give it an edge whose sides are inclined to one another, about as much as those of the letter V. The edge of a chisel is an obvious case in point; so also is the edge of a butcher's knife, which is given by applying it to the steel at a considerable inclination. A razor has only to cut hairs, and will splinter if used to mend a pen, yet even a razor is shaped like a wedge, that it may not receive too fine an edge when stropped with its face flat upon the hone.
Nails, Subst.i.tutes for.--Las.h.i.+ngs of raw hide supersede nails for almost every purpose. It is perfectly marvellous how a gunstock, that has been shattered into splinters, can be made as strong again as ever, by means of raw hide sewn round it and left to dry; or by drawing the skin of an ox's leg like a stocking over it. It is well to treat your bit of skin as though parchment (which see) were to be made of it, burying the skin and sc.r.a.ping off the hair, before sewing it on, that it may make no eyesore.
Tendons, or stout fish-skin such as s.h.a.green, may also be used on the same principle. An axle-tree, cracked lengthwise, can easily be mended with raw hide; even a broken wheel-tire may be replaced with rhinoceros or other thick hide; if the country to be travelled over be dry.
Sketch of lathe as described below].
Lathes may be wanted by a traveller, because the pulleys necessary for a large sailing-boat, and the screw of a carpenter's bench, cannot be made without one. The sketch will recall to mind the original machine, now almost forgotten in England, but still in common use on the Continent. It is obvious that makes.h.i.+ft contrivances can be set up on this principle, two steady points being the main things wanted. A forked bough suffices for a treadle. A very common Indian lathe consists of two tent-pegs, two nails for the points; a leather thong, and some makes.h.i.+ft hand-rest; neither pole nor treadle is used, but an a.s.sistant takes one end of the thong in one hand, and the other end in the other hand, and hauls away in a see-saw fas.h.i.+on. For turning hollows, a long spike is used instead of a short point: then, a hole is bored into the wood to the depth of the intended hollow, and the spike is pushed forward until it abuts against the bottom of the hole. One form of lathe is simplicity itself: two thick stakes are driven in the ground, so far apart as to include the object to be turned; a cross piece is lashed to them (by a creeper cut out of the jungle), for the double purpose of holding them together, and of serving as a rest for the gouge. The object is turned with a thong, as already described.
Charcoal, Tar, and Pitch.--Charcoal.--Dig a hole in the earth, or choose some gigantic burrow, or old well, and fill it with piles of wood, arranging them so as to leave a kind of chimney down the centre: the top of the hole is now to be covered over with sods excepting the chimney, down which a brand is dropped to set fire to the wood. The burning should be governed by opening or shutting the chimney-top with a flat stone; it should proceed very gradually, for the wood ought to smoulder, and never attain to a bright red heat: the operation will require from two days to a week. The tarry products of the wood drain to the bottom of the well.
Tar is made by burning larch, fir, or pine, as though charcoal had to be made; dead or withered trees, and especially their roots, yield tar most copiously. A vast deal is easily obtained. It collects at the bottom of the pit, and a hole with smooth sides should be dug there, into which it may drain. For making tar on a smaller scale:--ram an iron pot full of pine wood; reverse it and lay it upon a board pierced with a hole one inch in diameter; then prop the board over 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.--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.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 pus.h.i.+ng the mouth flat home, is ejected through the nozzle.
These bellows require no valve, and are the simplest that can be made: they are in use throughout India. The nozzle or tube to convey the blast may be made of a plaster of clay or loam, mixed with gra.s.s, and moulded round a smooth pole.
Metals, to work.--Iron Ore is more easily reduced than the ore of any other metal: it is usually sufficient to throw the ore into a charcoal-fire and keep it there for a day or more, when the pure metal will begin to appear.
Welding Composition for iron or steel, is made of borax 10 parts, sal ammoniac 1 part; to be melted, run out on an iron plate, and, when cold, pounded for use.
Cast Steel.--A mixture of 100 parts of soft iron, and two of lamp-soot, melts as easily as ordinary steel--more easily than iron. This is a ready way of making cast-steel where great heat cannot be obtained.
Case-hardening is the name given to a simple process, by which the outside of iron may be turned into steel. Small tools, fish-hooks, and keys, etc., are usually made of iron; they are fas.h.i.+oned first, and case-hardened afterwards. There are good reasons for this: first, because it is the cheapest way of making them; and secondly, because while steel is hard, iron is tough; and anything made of iron and coated with steel, combines some of the advantages of both metals. The civilised method of case-hardening, is to brighten up the iron and to cover it with prussiate of potash, either powdered or made into a paste. The iron is then heated, until the prussiate of potash has burned away: this operation is repeated three or four times. Finally, the iron, now covered with a thin layer of steel, is hardened by quenching it in water. In default of prussiate of potash, animal or even vegetable charcoal may be used, but the latter is a very imperfect subst.i.tute. To make animal charcoal, take a sc.r.a.p of leather, hide, hoof, horn, flesh, blood--anything, in fact, that has animal matter in it; dry it into hard chips like charcoal, before a fire, and powder it. Put the iron that is to be case-hardened, with some of this charcoal round it, into the midst of a lump of loam. This is first placed near the fire to harden, and then quite into it, where it should be allowed to slowly attain a blood-red heat, but no higher. Then, break open the lump, take out the iron, and drop it into water to harden.
Lead is very useful to a traveller, for he always has bullets, which furnish the supply of the metal, and it is so fusible that he can readily melt and cast it into any required shape; using wood, or paper, partly buried in the earth, for his mould. If a small portion of the lead remain unmelted in the ladle, the fluid is sure not to burn the mould. By attending to this a wooden mould may be used scores of times.