Table 145.-LIST OF WOODS AND THEIR USES. The Letter H. means Hard; M., Medium, and S., Soft. Acacia, H., fencing, turnery. Alder, H., sluices, pumps. Ash, H., wagons, implements. Boxwood, H., engraver's blocks. Cherry, Australasian, H., gun Ebony, H., rulers, cabinet work. Hickory, H., vehicles, wheel spokes. Hornbeam, H., teeth of wheels. Lancewood, H., fishing rods, bows. Lignum Vitæ, H., pestles, turnery. Mahogany, H., furniture. Poplar, M., furniture, turnery. Sassafras, H., turnery, screws. Sycamore, S., turnery, furniture. Tulip Wood, H., veneers, cabinet Walnut, H., furniture, gun stocks. blocks, cabinet work. Willow, S., baskets, spoons, &c. The most beautifully marked woods are rosewood, Italian walnut, Virginia walnut, Spanish mahogany, bird's eye maple, satin-wood, tulipwood, snake-wood, silver-wood, laburnum, olive-wood, lemon-wood, yew, oak, pitch-pine, and coromandel-wood. The most even and close-grained woods are ebony, myrtle, lime, box, olive, Virginia walnut, pear-tree, sycamore, cowrie-wood, beech, pine and holly. The most durable woods are oak, ebony, cedar, box, hornbeam, poplar, larch, chestnut, lignum vitæ, teak, elm, acacia, and yellow deal. The most elastic woods are lancewood, hickory, ash, hazel, snakewood, yew and chestnut. The scented woods are sandal-wood, sassafras, camphor-wood, cedar, rosewood and satin-wood. The dye-woods are logwood, saunders-wood, Brazil-wood, cane-wood, fustic, zante and green ebony. Qualities of Timber.-The most odoriferous kinds of woods are generally esteemed the most durable; also woods of a close and compact texture are generally more durable than those that are open and porous. In general, the quantity of charcoal afforded by woods offers a tolerably accurate indication of their durability; those most abundant in charcoal and earthy matter are most permanent; and those which contain the largest proportion of gaseous elements are the most destructible. The chestnut and the oak are pre-eminent as to durability, and the chestnut affords rather more carbonaceous matter than the oak. But this is not always the case, as red or yellow fir is as durable as the oak in many situations. An experiment to determine the comparative durability of different woods was made with planks of trees 1 inches thick of from thirty to forty-five years' growth; after standing ten years in the weather, they were examined and found to be in the following state :-* Cedar, perfectly sound. Chestnut, perfectly sound. Larch, the heart sound but sap quite Abele, or great white poplar, sound. This shows the kinds of woods best adapted to resist the weather, but even in the same kind of wood there is much difference in the durability; the timber of those trees which grow in moist and shady places is not so good as that which comes from a more exposed situation, nor is it so close, substantial, and durable. The best Oak Timber when new is of a pale brownish-yellow colour, with a faint shade of green, a glossy and firm surface. The more compact it is and the smaller the pores are the longer it will last; but the open, porous, and foxy-coloured oak is weak and not durable. Oak contains gallic acid which corrodes iron, therefore it should be fastened with either galvanised iron or copper screws. Oak shrinks about one thirty-second part of its width in seasoning, and warps and twists much in drying. Alder is extremely durable in water or wet ground, and is valuable for piles, pumps and sluices, and for any purpose where it is constantly wet, but it soon rots when it is exposed to the weather or to damp, and in a dry state it is much subject to worms. Elm is extremely durable in water and makes excellent piles and planking for wet foundations, and is used also for making pumps, keels of ships, &c. Old London Bridge stood upon piles of elm, which remained six centuries without material decay. Beech is durable when constantly immersed in water and is useful for piles in situations where it will be constantly wet, but it rots quickly in damp places and is soon injured by worms. * See "Carpentry and Joinery." Crosby Lockwood & Co. Ash is durable in a dry situation, but soon rots when exposed to either damp or alternate dryness and moisture. Ash is superior to any other British timber for toughness and elasticity. The strength of timber to resist breaking strains in tension and compressure is given at page 271. The tenacity along the grain is greatest in those woods which have the straightest and most distinctly marked fibres. The tenacity across the grain is about in pine-wood, and in leafwood of the tenacity along the grain. The resistance to crushing along the grain depends upon the resistance of the fibres to being split asunder. It averages from 50 to 70 per cent. of the tenacity for dry timber, and half that per-centage for green timber. The resistance to crushing across the grain is considerably less than the resistance to crushing along the grain, in all woods excepting lignum-vitæ, which resists a crushing force with nearly equal strength along and across the grain. Ebony, iron-wood, and box-wood also offer considerable resistance to crushing across the grain. The toughest wood is that which bears the greatest load and bends the most at the time of fracture. The following list shows the comparative toughness of various kinds of timber. Ash being 100; beech is 85; cedar of Lebanon, 84; larch, 83; sycamore and common walnut, each 68; occidental plane, 66; oak, hornbeam, alder, and Spanish mahogany, each '62; teak and acacia, each 58; elm and young chestnut, each ·52. Trees should not be cut down before they arrive at maturity. If cut down before maturity a great part of the tree is sap-wood and the heart-wood is deficient in strength and durability; if allowed to grow beyond maturity the wood is brittle, discoloured, devoid of elasticity, and soon decays. An oak tree arrives at maturity at 100 years of age; the average quantity of timber produced by a tree of that age is about 75 cubic feet; and it should not be felled at a less age than 60 years. Poplars should be cut down when the trees are between 30 and 50 years old; ash, larch, and elm between 50 and 100 years old, and the Norway spruce and Scotch pine between 70 and 100 years old. Measuring Timber.-To find the Solidity of Round or Unsquared Timber.-Rule: Multiply the square of of the circumference-or quarter girth-by the length, and the product will be the content. If the tree tapers regularly the girth must be taken in the middle of the tree. When the taper is not regular several girths must be taken, and their sum divided by their number will give the mean girth, which must be used in the above rule. An allowance for the bark, of from inch to inch for every foot of the quarter girth for ash, elm, beech, and young oak, and of from 1 inch to 2 inches for old oak, is usually deducted from the girth. To find the Solidity of Squared or Four-sided Timber.-Rule: Multiply the mean breadth by the mean thickness, and multiply the product by the length. Table 146.-LIST OF MINERALS.* Arsenical Iron, an ore containing variable proportions of iron, arsenic, and sulphur, used in the manufacture of white arsenic. Azurite, a valuable azure blue ore of copper, containing about 55 per cent. copper, with carbonic acid and water. Bismuth Ochre, an oxide of bismuth found in Saxony, Bohemia, and Siberia. Bornite, the principal Chilian ore of copper, containing about 59 per cent. copper, with iron and sulphur. Cassiterite, or Tinstone, the commonest ore of tin, containing about 93 per cent. pure tin. Ceruscite, an ore of lead, containing about 83 per cent. metal. Chalcoite, an ore of copper, 75 per cent. metal, with sulphur. Chalcopyrite, copper 33, iron 33, sulphur 33 per cent., the principal ore in Cornwall. Chromic Iron the ore of chromium, containing chromium from 27 to 40 Chromite 5 per cent., with iron and other metals. Cinnabar, sulphide of mercury; the common ore yields about 80 per cent. metal. Cobaltite, cobalt 33 per cent., with iron, arsenic, and sulphur. Copper Pyrites, see Chalcopyrite, Cuprite, a Chilian ore of copper, containing about 88 per cent. of metal. Franklinite, an uncommon ore of iron and zinc, containing iron 45, manganese 9, zinc 20, oxygen 26. Galenite, the only important ore of lead, containing about 75 per cent. of metal, with sulphur and sometimes silver, gold, and other metals. Hematite, one of the commonest iron ores, containing about 75 per cent. metal, and called by different names. Ilmenite, titaniferous iron ore, sometimes containing gold. Iron Glance, specular iron ore, q. v. Iron Minium, red ochre, q. v. Kidney Ore, a hard bubble-shaped form of hematite iron ore. Limonite, the iron mineral which is the basis of bog ores, ochres, &c., containing about 60 per cent. metal. Magnetic Iron Ore the most valuable and common ore of iron, con- Malachite, a valuable copper ore, containing about 50 per cent. of metal, much used for ornaments. Manganite, an ore of manganese, containing about 62 per cent. Micaceous Iron Ore, a scaly variety of hematite. Millerite, an ore of nickel, containing 64 per cent., with sulphur. Minium, one of the scarcer ores of lead, containing 90 per cent. of metal, with oxygen. * This list of minerals is extracted from "The Ironmonger's Diary." Niccolite, an important ore of nickel, containing 44 per cent. of metal, with arsenic. Oligiste, a specular iron ore, q. v. Orpiment, a lemon-yellow arsenic ore, containing 61 arsenic, with 39 sulphur; not much used as ore. Puddlers' Ore, an unctuous form of hematite used in Cumberland for lining the hearths of puddling furnaces. Pyrite, a variable ore of iron, containing iron about 42, with sulphur and other metals. Pyrolusite, an ore of manganese, used in glass and bleaching powder making, containing about 60 per cent. manganese. Realgar, a bright red sulphide of arsenic. Red Hematite, the smelter's name for all iron ores consisting chiefly of anhydrous peroxide of iron. Red Ochre, a compact earthy variety of hematite. Rother Glaskopf, kidney ore (iron). Siderite, an important ore of iron, consisting of ferrous carbonate. Smaltite, an ore of cobalt, found in Saxony, used for making smalt. Smithsonite, a carbonate of zinc, much used as an ore, containing about 50 per cent. metal. Specular Iron Ore, brilliant crystallised hematite. Sphalerite, an abundant ore of zinc, containing about 60 per cent., with sulphur and other metals. Stibium) the principal ore of antimony, containing about 70 per cent. of Stibnite metal; the black antimony of the shops is this, fused. Tetrahedrite, an ore of copper of variable composition, containing 19 to 25 per cent. of copper, with sulphur and other metals. Tin Stone, cassiterite. Titaniferous Iron Ore, ilmenite. Wad, black manganese ore, of variable composition. Table 147.-DESCRIPTION OF CHEMICAL AND MINERAL SUBSTANCES. Acetate of Copper is verdigris. Alum is sulphate of aluminia. Aquafortis is nitric acid. Bleaching Powder is chloride of lime and hydrochloric acid. Blue Billy for lining furnaces, is pure oxide of iron Blue Stone or Blue Vitriol is sulphate of copper. Boiler Scale is carbonate of calcium. Burnett's Disinfecting Fluid is chloride of zinc solution. Calcium is the metallic base of lime. |