DACTYLUS, a Greek measure of length, the sixteenth part of an English foot. Dado, a term for the die or plane face of a pedestal. The dado employed in the interior of buildings is a continuous pedestal, with a plinth and base moulding, and a cornice or dado moulding surmounting the die. Dado, the solid block or cube forming the body of a pedestal, in classical architecture, between the base mouldings and cornice; an architectural arrangement of mouldings, etc., round the lower part of the walls of a room. Dagger, in ship-building, a piece of timber that crosses all the poppets of the bulge-ways, to keep them together: the plank that secures the heads of the poppets is called the dagger-plank. Dagger knees are lodging knees, with sille arms cast down and bolted through the clamp: they are placed at the lower decks of some ships, instead of hanging knees, to preserve as much stowage in the hold as possible. Daguerreotype, sun drawing; nature's drawing by the aid of light. It was the invention of two Frenchmen, M. Daguerre and M. Niepce. The invention consists of the fixation of the images formed on the focus of the camera-obscura; is made on very smooth surfaces of pure silver plated on copper. Dairy-house, a place for keeping milk. Dais, in early domestic architecture, D. the chief seat at the high board or principal table (cross-table) in a baronial hall; also the principal | table itself, and the raised part of the floor on which it is placed. Dais, a canopy to cover an altar, throne, or tribunal; the chief or upper table in a monastery. Dam, a bank or obstruction built across a river or stream, for the purpose of raising the level of the water on the opposite side of it. Dams built for the purpose of inland navigation, or for that of securing a water power, may be considered as having a more permanent character. Damascus steel, a sort of steel brought from the Levant, greatly esteemed for the manufacture of cutting instruments. Damasquine, a term applied to ornamental work of gold or silver, incrusted on iron or steel. Damonico or Monicon, an iron ochre, being a compound of terra di sienna and Roman ochre, burnt, and having all their qualities: it is rather more russet in hue than the orange de Mars, has considerable transparency, is rich and durable in colour, and affords good flesh tints. Damper, a valve placed in a chimney, to diminish the draught when the heat is too intense. Damper, in locomotive engines, a kind of iron Venetian blind, fixed to the smoke-box end of the boiler, in front of the tubes: it is shut down when the engine is standing, and thus stops the draught and economizes fuel; but it is opened when the engine is running. Damps: various kinds of permanently elastic fluids generated in mines are thus named by the miners: choke-damps consist mostly of carbonic acid gas, and fire-damps of carburetted hydrogen gas. Dancette, in heraldry, zigzag or chevron fret ; seen in Norman buildings. Dark ages were periods when the monks and ecclesiastics were the only learned persons: when religion, law, politics, and physics were administered and controlled by the clergy, denominated clerks. Data useful in various calculations of the properties of materials. [The data correspond to the mean tem perature and pressure of the atmosphere; the materials are assumed to be dry, and the temperature is measured by Fahrenheit's scale.] AIR. Specific gravity, 0·0012; weight of a cubic foot, 0-0753 lbs., or 527 grains (Shuckburgh); 13:3 cubic feet, or 17 cylindric feet of air, weigh 1 lb.; it expands or 00208 of its bulk at 32° by the addition of one degree of heat. (Dulong and Petit.) ASH. Specific gravity, 0·76; weight of a cubic foot, 47.5 lbs. ; weight of a bar 1 foot long and 1 inch square, 0.33 lbs.; will bear without permanent alteration a strain of 3540 lbs. upon a square inch, and an extension of of its length; weight of modulus of elasticity for a base of an inch square, 1,640,000 lbs.; height of modulus of elasticity, 4,970,000 feet; modulus of resilience, 76; specific resilience, 10. (Calculated from Barlow's experiments.) Compared with cast iron as unity, its strength is 0.23; its extensibility, 26; and its stiffness, 0·089. ATMOSPHERE. Mean pressure of, at London, 28.89 inches of mercury 14.18 lbs. upon a square inch. (Royal Society.) The pressure of the atmosphere is usually estimated at 30 inches of mercury, which is very nearly 134 lbs. upon a square inch, and equivalent to a column of water 34 feet high. BEECH. Specific gravity, 0·696; weight of a cubic foot, 45.3 lbs. ; weight of a bar 1 foot long and 1 inch square, 0.315 lb.; will bear without permanent alteration on a square inch, 2360 lbs., and an extension of of its length; weight of modulus of elasticity for a base of an inch square, 1,345,000 lbs. ; height of modulus of elasticity, 4,600,000 feet; modulus of resilience, 414; specific resilience, 6. (Calculated from Barlow's Experiments.) Compared with cast iron as unity, its strength is 0.15; its extensi bility, 21; and its stiffness, 0-073. BRASS, cast. Specific gravity, 8.37; weight of a cubic foot, 523 lbs.; weight of a bar 1 foot long and 1 inch square, 3-63 lbs. ; expands of its length by one degree of heat (Troughton); melts at 1869° (Daniell); cohesive force of a square inch, 18,000 lbs. (Rennie); will bear on a square inch without permanent alteration, 6700 lbs., and an extension in length of; weight of modulus of elasticity for a base of an inch square, 8,930,000 lbs.; height of modulus of elasticity, 2,406,000 feet; modulus of resilience, 5; specific resilience, 0·6. (Tredgold). Compared with cast iron as unity, its strength is 0-435; its extensibility, 0.9; and its stiffness, 0'49. BRICK. Specific gravity, 1841; weight of a cubic foot, 115 lbs. ; absorbs of its weight of water; cohesive force of a square inch, 275 lbs. (Tredgold); is crushed by a force of 562 lbs. on a square inch (Rennie.) BRICK-WORK. Weight of a cubic foot of newly built, 117 lbs.; weight of a rod of new brick-work, 16 tons. BRIDGES. When a bridge is covered with people, it is about equivalent to a load of 120 lbs. on a superficial foot; and this may be esteemed the greatest possible extraneous load that can be collected on a bridge; while one incapable of supporting this load cannot be deemed safe. BRONZE. See Gun-metal. CAST IRON. Specific gravity, 7.207; weight of a cubic foot, 450 lbs.; a bar 1 foot long and 1 inch square weighs 3.2 lbs. nearly; it expands 100 of its length by one degree of heat (Roy); greatest change of length in the shade in this climate, 2; greatest change of length when exposed to sun's rays, melts at 3479° (Daniell), and shrinks in cooling from to of its length (Muschet); is crushed by a force of 93,000 lbs. upon a square inch (Rennie); will bear without permanent alteration 15,300 lbs. upon a square inch, and an extension of of its length; weight of modulus of elasticity, for a base 1 inch square, 18,400,000lbs.; height of modulus of elasticity, 5,750,000 feet; modulus of resibence, 127; specific resilience, 1-76. (Tredgold.) CHALK. Specific gravity, 2-315; weight of a cubic foot, 144-7 lbs. ; is crushed by a force of 500 lbs. on a square inch. (Rennie.) CLAY. Specific gravity, 2.0; weight of a cubic foot, 125 lbs. COAL, Newcastle. Specific gravity, 1-269; weight of a cubic foot, 79 31 lbs. A London chaldron of 36 bushels weighs about 28 cwt., whence a bushel is 87 lbs. (but is usually rated at 84 lbs.) A Newcastle chaldron, 53 cwt. (Smeatoo.) COPPER. Specific gravity, 8.75 (Hatchett); weight of a cubic foot, 549 lbs.; weight of a bar 1 foot long and 1 inch square, 3.81 lbs. ; expands in length by one degree of beat. 356 (Smeaton); melts at 2548° (Daniell); cohesive force of a square inch, when hammered, 33,000 lbs. (Rennie.) EARTH, common. Specific gravity, 152 to 2:00; weight of a cubic foot, from 95 to 125 lbs. ELM. Specific gravity, 0.544; weight of a cubic foot, 34 lbs. ; weight of a bar I foot long and 1 inch square, 0-236 lbs.; will bear on a square inch without permanent alteration, 3240 lbs., and an extension in length of ; weight of modulus of elasticity for a base of an inch square, 1,340,000 lbs. ; height of modulus of elasticity, 5,680,000 feet; modulus of resihence, 7-87; specific resilience, 14-4. (Calculated from Barlow's Experiments.) Compared with cast iron as unity, its strength is 0.21; its extensibility, 29; and its stiffness, 0-073. FIR, red or yellow. Specific gravity, 0.557; weight of a cubic foot, 34.8 lbs.; weight of a bar 1 foot long and 1 inch square, 0-242 lb. ; will bear on a square inch without permanent alteration, 4290 lbs. = 2 tons nearly, and an extension in length of weight of modulus of elasticity for a base of an inch square, 2,016,000 lbs. ; height of modulus of elasticity, 8,330,000 feet; modulus of resilience, 9.13; its specific resilience, 164. (Tredgold.) Compared with cast iron as unity, its strength is 0.3; its extensibility, 2-6, and its stiffness, 0-1154, = 888. FIR, white. Specific gravity, 0.47; weight of a cubic foot, 29-3 lbs. ; weight of a bar 1 foot long and 1 inch square, 0.204 lb. ; will bear on a square inch without permanent alteration, 3630 lbs., and an extension in length of; weight of modulus of elasticity for a base of an inch square, 1,830,000 lbs. ; height of modulus of elasticity, 8,970,000 feet; modulus of resilience, 7.2; specific resilience, 15·3. (Tredgold.) Compared with cast iron as unity, its strength is 0-23; its extensibility, 24; and its stiffness, 0·1. FLOORS. The weight of a superficial foot of a floor is about 40 lbs. when there is a ceiling, counterfloor, and iron girders. When a floor is covered with people, the load upon a superficial foot may be calculated at 120 lbs.: therefore, 120+40=160 lbs. on a superficial foot is the least stress that ought to be taken in estimating the strength for the parts of a floor of a room. FORCE. See Gravity, Horse, etc. GRANITE, Aberdeen. Specific gravity, 2.625; weight of a cubic foot, 164 lbs. ; is crushed by a force of 10-910 lbs. upon a square inch. (Rennie.) GRAVEL. Weight of a cubic foot, about 120 lbs. GRAVITY generates a velocity of 32 feet in a second in a body falling from rest; space described in the first second, 16 feet. GUN-METAL, cast (copper 8 parts, tin 1). Specific gravity, 8-153; weight of a cubic foot, 509 lbs.; weight of a bar 1 foot long and 1 inch square, 3.54 lbs. (Tredgold); expands in length by 1° of heat, (Smeaton); will bear on a square inch without permanent alteration, 10,000 lbs., and an extension in length of weight of modulus of elasticity for a base 1 inch square, 9,873,000 lbs.; height of modulus of elasticity, 2,790,000 feet; modulus of resilience, and specific resilience, not determined. (Tredgold.) Compared with cast iron as unity, its strength is 0.65; its extensibility, 1-25; and its stiffness, 0.535. HORSE, of average power, produces the greatest effect in drawing a load when exerting a force of 187 lbs. with a velocity of 2 feet per second, working 8 hours in a day. (Tredgold.) A good horse can exert a force of 480 lbs. for a short time. (Desaguliers.) In calculating the strength for horse machinery, the horse's power should be considered 400 lbs. IRON, cast. See Cast Iron. Iron, malleable. Specific gravity, 7.6 (Muschenbroek); weight of a cubic foot, 475 lbs.; weight of a bar 1 foot long and 1 inch square, 3.3 lbs.; ditto, when hammered, 3-4 lbs.; expands in length by 1° of heat, 000 (Smeaton); good English iron will bear on a square inch without permanent alteration, 17,800 lbs. = 8 tons nearly, and an extension in length of sive force diminished by an elevation 1° of temperature; weight of modulus of elasticity for a base of an inch square, 24,920,000 lbs. ; height of modulus of elasticity, 7,550,000 feet; modulus of resilience, and specific resilience, not determined. (Tredgold.) cohe Compared with cast iron as unity, its strength is 1.12; its extensibility, 0-86; and its stiffness, 1·3. LARCH. Specific gravity, 560; weight of a cubic foot, 35 lbs. ; weight of a bar 1 foot long and 1 inch square, 0-243 lb.; will bear on a square inch without permanent alteration, 2065 lbs., and an extension in length of; weight of modulus of elasticity for a base of an inch square, 10,074,000 lbs. ; height of modulus of elasticity, 4,415,000 feet; modulus of resilience, 4; specific resilience, 7.1. (Calculated from Barlow's Experiments.) Compared with cast iron as unity, its strength is 0.136; its extensibility, 23; and its stiffness, 0-058. LEAD, cast. Specific gravity, 11:353 (Brisson); weight of a cubic foot, 709-5 lbs.; weight of a bar 1 foot long and 1 inch square, 4.94 lbs. ; expands in length by I degree of heat, 200 (Smeaton); melts at 612° (Crichton); will bear on a square inch without permanent alteration, 1500 lbs., and an extension in length of weight of modulus of elasticity for a base 1 inch square, 720,000 lbs. ; height of modulus of elasticity, 146,000 feet; modulus of resilience, 312; specific resilience, 0.27 (Tredgold). Compared with cast iron as unity, its strength is 0.096; extensibility, 2.5; and its stiffness, 0·0385. MAHOGANY, Honduras. Specific gravity, 0.56; weight of a cubic foot, 35 lbs.; weight of a bar 1 foot long and 1 inch square, 0-243 lb. ; will bear on a square inch without permanent alteration, 3800 lbs., and an extension in length of weight of modulus of elasicity for a base 1 inch square, 1,596,000 lbs.; height of modulus of elasticity, 6,570,000 feet; modulus of resi lience, 9-047; specific resilience, 16 1. (Tredgold.) Compared with cast iron as unity, its strength is 0.24; its extensibility, 29; and its stiffness, 0'487. MAN. A man of average power produces the greatest effect when exerting a force of 314 lbs. with a velocity of 2 feet per second, for 10 hours in a day. (Tredgold.) A strong man will raise and carry from 250 to 300 lbs. (Desaguliers.) MARBLE, white. Specific gravity, 2.706; weight of a cubic foot, 169 lbs; weight of a bar 1 foot long and 1 inch square, 1·17 lb. ; cohesive force of a square inch, 1811 lbs. ; extensibility, of its length; weight of modulus of elasticity for a base of an inch square, 2,520,000 lbs. ; height of modulus of elasticity, 2,150,000 feet; modulus of resilience at the point of fracture, 13; specific resilience at the point of fracture, 0:48 (Tredgold); is crushed by a force of 6060 lbs. upon a square inch (Rennie). MERCURY. Specific gravity, 13-568 (Brisson); weight of a cubic inch, 0'4948 lb.; expands in bulk by 1° of heat, (Dulong and Petit); weight of modulus of elasticity for a base of an inch square, 4,417,000 lbs.; height of modulus of elasticity, 750,000 feet. (Dr. Young, from Canton's Experiments.) OAK, good English. Specific gravity, 0-83; weight of a cubic foot, 52 lbs.; weight of a bar 1 foot long and 1 inch square, 0-36 lb. ; will bear upon a square inch without permanent alteration, 3960 lbs., and an extension in length of weight of modulus of elasticity for a base I inch square, 1,700,000 lbs.; height of modulus of elasticity, 4.730,000 feet; modulus of resilience, 9-2; specific resilience, 11. (Tredgold.) Compared with cast iron as unity, its strength is 0-25; its extensibility. 28; and its stiffness, 0·093. PENDULUM. Length of pendu lum to vibrate seconds in the latitude of London, 39-1372 inches (Kater); ditto to vibrate halfseconds, 9-7843 inches. PINE, American yellow. Specific gravity, 0:46; weight of a cubic foot, 26 lbs. ; weight of a bar 1 foot long and one inch square, 0-186 lb.; will bear on a square inch without permanent alteration, 3900 lbs., and an extension in length of weight of modulus of elasticity for a base of an inch square, 1,600,000 lbs. ; height of modulus of elasticity, 8,700,000 feet; modulus of resilience, 9.4; specific resilience, 20. (Tredgold.) Compared with cast iron as unity, its strength is 0-25; its extensibility, 29; and its stiffness, 0.087. PORPHYRY, red. Specific gravity, 2.871; weight of a cubic foot, 179 lbs. ; is crushed by a force of 35,568 lbs. upon a square inch. (Gauthey.) ROPE, hempen. Weight of a common rope 1 foot long and i inch in circumference, from 0.04 to 0.46 lb.; and a rope of this size should not be exposed to a strain greater than 200 lbs. ; but in compounded ropes, such as cables, the greatest strain should exceed 120 lbs.; and the weight of a cable 1 foot in length and 1 inch in circumference does not exceed 0-027 lb. The square of the circumference in inches multiplied by 200 will give the number of pounds a rope may be loaded with; and multiply by 120 instead of 200 for cables. Common ropes will bear a greater load with safety after they have been some time in use, in consequence of the tension of the fibres becoming equalized by repeated stretchings and partial untwisting. It has been imagined that the improved strength was gained by their being laid up in store; but if they can there be preserved from deterioration, it is as much as can be expected. Roofs. Weight of a square foot of Welsh rag slating, 114 lbs.; weight of a square foot of plain tiling, 16 lbs.; greatest force of the wind |