a single reed, they would obstruct each other in rising and sinking, and the shed would not be sufficiently open to allow the shuttle a free passage. To avoid this inconvenience, other reeds are placed behind that which strikes up the weft; and the warp threads are so disposed, that those which pass through the same interval in the first reed are divided in passing through the second, and again in passing through the third. By these means the obstruction, if not entirely removed, is greatly lessened. In the weaving of plain thick woollen cloths, to prevent obstructions of this kind, arising from the closeness of the set, and roughness of the threads, only one-fourth of the warp is sunk and raised by one treddle, and a second is pressed down to complete the shed, between the times when every shot of weft is thrown across. Double cloth is composed of two webs, each of which consists of separate warp and separate weft; but the two are interwoven at intervals. The junction of the two webs is formed by passing each of them occasionally through the other, so that each particular part of both is sometimes above and sometimes below. This species of weaving is almost exclusively confined to the manufacture of carpets in this country. The material employed is dyed woollen; and, as almost all carpets are decorated with fanci ful ornaments, the colours of the two webs are different, and they are made to pass through each other, at such intervals as will form the patterns required. Hence it arises, that the patterns of each side of the carpet are the same, but the colours are reversed. Carpets are usually woven in the draw-loom. Gauze differs in its formation from other cloths, by having the threads of the warp crossed over each other, instead of lying parallel. They are turned to the right and left alternately; and each shot of weft preserves the twine which it has received. This effect is caused by a singular mode of producing the sheds, which cannot easily be described without the aid of drawings. Cross, or net-weaving, is a separate branch of the art, and requires a loom particularly constructed for the purpose. Spots, Brocades, and Lappets, are produced, by a combination of the arts, of plain, tweeled, and gauze weaving; and, as in every other branch of the art, are produced in all their varieties by different ways of forming the sheds, by the apVOL. XII. plication of heddles, and their connections with the treddles which move them. Indeed, the whole knowledge of the art consists in this part of the apparatus of a loom. In drawing up the foregoing account of the art of weaving, we have laboured under inconveniences of no small magnitude. The many different kinds of cloth; the almost infinite variety of ways, though all on the same general principle, of constructing them; the different formation of apparatus in making different cloths; and, lastly, the want of uniformity in the technical phraseology of the art, have all tended to render our descriptions far more intricate and difficult than they otherwise would have been. The assistance, however, which we have derived from the very excellent "Essays on the Art of Weaving," by Mr. Duncan, ought not to pass by us unacknowledged. It is a most curious and valuable publication, embracing almost every thing necessary to be known concerning the art on which it professes to treat. WEBERA, in botany, a genus of the Pentandria Monogynia class and order. Essential character: contorted; berry inferior, two-celled; cells one-seeded; style elevated; stigma club-shaped; calyx five-cleft. There are three species. WEDGE, one of the mechanical powers, as they are called. The wedge is a triangular prism, whose bases are equi. lateral acute-angled triangles. See ME CHANICS. WEEK, in chronology, a division of time comprising seven days. See CHRO NOLOGY. WEIGELIA, in botany, so named in honour of Christ. Ehrenfr. Weigel; a ge nus of the Pentandria Monogynia class and order. Essential character: calyx five-leaved; corolla funnel-form; style from the base of the germ; stigma peltate; seed one. There are two species, viz. W. japonica, and W. corœensis, both natives of Japan. WEIGHT, in physics, is a quality in natural bodies, by which they tend to wards the centre of the earth. See GRA. VITATION. Weight may be distinguish. ed into absolute, specific, and relative. It is demonstrated by Sir Isaac Newton, 1. That the weights of all bodies, at equal distances from the centre of the earth, are proportional to the quantities of matter that each contains. 2. On dif ferent parts at the earth's surface, the weight of the same body is different; owing to the spheroidal figure of the H h earth, which causes the bodies on the surface to be nearer the centre in going from the equator towards the poles; and the increase of weight is nearly in proportion to the square of the sine of the latitude: the weight at the equator to that at the pole being as 229 230; or the whole increase of weight from the equator to the pole is the 229th part of the former. 3. That the weights of the same body, at different distances above the earth, are inversely as the squares of the distances from the centre. So that a body at the distance of the moon, which is 60 semi-diameters from the earth's centre, would weigh onlyth part of what it weighs at the surface of the earth. 4. That at different distances within the earth, or below the surface, the weights of the same body are directly as the distances from the earth's centre; so that at half way toward the centre a body would weigh but half as much, and at the centre it would weigh nothing at all. 5. A body immersed in a fluid, which is specifically lighter than itself, loses so much of its weight as is equal to the weight of a quantity of the fluid of the same bulk with itself. Hence a body loses more of its weight in a heavier fluid than in a lighter one, and therefore it weighs more in a lighter fluid than in a heavier one. The weight of a cubic foot of water is 1000 ounces, or 6246. avoirdupois; this, multiplied by 32, gives 2000lb. the weight of a ton: hence eight cubic feet formerly made a hogshead, and four hogsheads a ton, in capacity as well as in weight. Measures for corn, coals, and other dry articles, were constructed on the same principle. A bushel of wheat, assumed as a general standard for all sorts of grain, weighed 621⁄2., eight of these make a quarter, and four quarters, or 32 bushels, a ton weight. Coals were sold by the chaldron, and supposed to weigh a ton, though in reality it weighs much more. Hence a ton weight is the common standard for liquids, wheat, and coals. Had this analogy been adhered to, the confusion which is occasioned by different local weights would have been avoided. To regulate the weights and measures of a country is a branch of the sovereign's prerogative. For the public convenience, these ought to be universally the same throughout the nation, the better to reduce the prices of articles to equivalent values. But as weight and measure are things in their nature arbitrary and uncertain, it is necessary that they be reduced to some fixed rule or standard. It is, however, impossible to fix such a standard by any written law or oral proclamation, as no person can, by words only, give to another an adequate idea of a pound weight, or foot rule. It is therefore expedient to have recourse to some visible, palpable, material standard, by forming a comparison, with which all weights and measures may be reduced to one uniform size. Such a standard was anciently kept at Winchester; and we find in the laws of King Edgar, nearly a century before the conquest, an injunction that this measure should be observed throughout the realm. Most nations have regulated the standard of measures of length from some parts of the human body. as the palm, the hand, the span, the foot, the cubit, the ell, (ulna, or arm,) the pace, and the fathom. But as these are of different dimensions in men of different proportions, ancient historians inform us, that a new standard of length was fixed by our king Henry the First; who commanded that the ulna, or ancient ell, which answers to the modern yard, should be made of the exact length of his own arm. See MEA SURE. The standard of weights was originally taken from grains or corns of wheat, whence our lowest denomination of weights is still called a grain; thirty-two of which are directed, by the statute called" compositio mensurarum," to compose a pennyweight, twenty of which make an ounce, and twelve ounces a pound, &c. Under King Richard the First it was ordained, that there should be only one weight and one measure throughout the nation, and that the custody of the assize, or standard of weights and measures, should be committed to certain persons in every city and borough; from whence the ancient office of the king's ulnager seems to have been derived. These original standards were called pondus regis, and mensura domini regis, and are directed, by a variety of subsequent statutes, to be kept in the exchequer chamber, by an officer called the clerk of the market, except the wine gallon, which is committed to the city of London, and kept in Guildhall. The Scottish standards are distributed among the oldest boroughs. The elward is kept at Edinburgh, the pint at Stirling, the pound at Lanark, and the firlot at Linlithgow. The two principal weights established in Great Britain are, troy weight and avoirdupois weight, as before mentioned. Under the head of the former it may further be added, that a carat is a weight of four grains; but when the term is applied to gold, it denotes the degree of fineness. Any quantity of gold is supposed divided into twenty-four parts. If the whole mass is pure gold, it is said to be twentyfour carats fine; if there are twentythree parts of pure gold, and one part of alloy or base metal, it is said to be twenty-three carats fine, and so on. Pure gold is too soft to be used for coin. The standard coin of this kingdom is 22 carats fine. A pound of standard gold is coined into 44 guineas, and therefore every guinea should weigh 5 dwts. 933 grains. A pound of silver for coin contains 11 oz. 2 dwts. pure silver, and 18 dwts. alloy; and standard silver plate 11 ounces pure silver, with one ounce alloy. A pound of standard silver is coined into 62 shillings, and therefore the weight of a shilling should be 3 dwts. 202 grains. Under the words avoirdupois and troy will be found an account of those weights; here we may add a small table from Mr. Ferguson, which gives a more enlarged comparison between these two weights. 175 Troy pounds are equal to 144 avoirdupois pounds. 175 Troy ounces are equal to 192 avoirdupois ounces. 1 Troy pound contains 5760 grains. 1 Avoirdupois ounce contains 437 1 Avoirdupois drachm contains 27.34375 1 Troy pound contains 13 oz. 2.651428576 drachms avoirdupois. 1 Avoirdupois lb. contains 1 lb. 2 oz. 11 dwts. 16 grs. troy. Therefore the avoirdupois lb. is to the lb. troy as 175 to 144, and the avoirdupois oz. is to the troy oz. as 437 is to 480. The moneyers, jewellers, &c. have a particular class of weights for gold and precious stones, viz. carat and grain, and for silver, the pennyweight and grain. The moneyers have also a peculiar subdivision of the troy grain: thus dividing The grain into 20 mites, The dealers in wool have likewise a particular set of weights: viz. the sack, Correspondence of English weights with those used in France before the revolution. The Paris pound, poids de marc of Charlemagne, contains 9216 Paris grains : it is divided into 16 ounces, each ounce into 8 gros, and each gros into 72 grains. It is equal to 7561 English troy grains. The English troy pound of 12 ounces contains 5760 English troy grains, and is equal to 702 Paris grains. The English avoirdupois pound of 16 ounces contains 7000 English troy grains, and is equal to 8538 Paris grains. To reduce Paris grains to English troy grains, divide by To reduce English troy grains to Paris grains, multiply by To reduce Paris ounces to English troy, divide by 256 = 7000 1 16 437.5 grammes. =453.25 >1.2189 1.015734 To reduce Eng. troy ounces to Paris, multiply by. Or the conversion may be made by means of the following tables. 1. To reduce French to English troy weight. The Paris pound = 7561 The ounce = 472 5624 English The gros The grain - .8204) SWEDISH WEIGHTS, Used by Bergman and Scheele. The Swedish pound, which is divided like the English apothecary, or troy pound, weighs 6556 grains troy. The kanne of pure water, according to Bergman, weighs 42250 Swedish grains, and occupies 100 Swedish cubical inches. Hence the kanne of pure water weighs 48088.719444 English troy grains, or is equal to 189.9413 English cubic inches; and the Swedish longitudinal inch is equal to 1.238435 English longitudinal inches. From these data, the following rules are deduced: 1. To reduce Swedish longitudinal inches to English, multiply by 1.2384, or divide by 0.80747. 2. To reduce Swedish to English cubical inches, multiply by 1.9, or divide by 0.5265. 3. To reduce the Swedish pound, ounce, drachm, scruple, or grain, to the corresponding English troy denomination, multiply by 1.1382, or divide by 8.786. 4. To reduce Swedish kannes to English wine pints, multiply by .1520207, or divide by 6.57804. 5. The lod, a weight sometimes used by Bergman, is the 32d part of the Swedish pound: therefore, to reduce it to the English troy pound, multiply by .03557, or divide by 28.1156. red that the length of a pendulum which should vibrate seconds would be proper to be made a universal standard for length, whatever the denomination should be fixed on, whether yard, or any thing else. It was however found, that it would be difficult in practice to measure and determine the true length of such a pendulum, that is, the exact distance between the point of suspension and the point of oscillation. Another cause of inaccuracy was afterwards discovered, when it was found that the second's pendulum was of different lengths in all the different latitudes, owing to the spheroidal figure of the earth, (See EARTH,) which is the cause why places in different latitudes, at different distances from the centre, and of course the pendulums, are acted upon by different forces of gravity, and therefore require to be of different lengths. In the latitude of London this is found to be 391 inches nearly. The Society of Arts, &c. have offered premiums for a plan that might accomplish this great object; and among other devices then brought forward was one by Mr. Hatton, which consisted in measuring the difference of the lengths of two pendulums at different times of vibration, which could be performed more easily and accurately than that of the length of one single pendulum. This method was put in practice, and fully explained and illustrated by the late Mr. Whitehurst, in his attempts to ascertain an universal standard of weights and measures. same kind of inaccuracy of measurement The Universal Standard for Weights and Mea- obtains in this way, though in a smaller sures. This is an object of vast importance, could it be attained: we fear, however, that, like a project for universal peace and good will among men, it is a thing rather to be desired than expected, in the present state of things. Philosophers may speculate on the importance and excellence of such a scheme, but statesmen, busy in projects of ambition, have not leisure to attend to any thing that does not augment their power, extend their influence, and render them rather a terror to mankind, than the objects of their praise and veneration. It behoves us, however, to give, in few words, a sketch of what has been attempted, with a view to an universal standard for weights and measures through the whole world. The plans laid down have been deduced from philosophical principles. After the invention of pendulum clocks, it occur * degree, as in a single pendulum. Another method has been proposed, on observing very accurately the space that a heavy body falls freely through in one second of time. Here absolute accuracy is almost unattainable; besides, the form of the earth introduces difficulties, owing to the different distances from the centre, and the consequent diversity in the force of gravity by which the body falls. This space, in the latitude of London, has been found 193 inches, of course it is different in other latitudes. The method of late years, proposed by the French, is that of measuring a degree on the earth's surface, at the latitude of 45 degrees, and from this to deduce an universal measure of lengths, which would be easily appli cable to weights also. WEIGHTS and MEASURES, in law. The standard of measures was originally kept at Winchester, which measure was by the law of King Edgar ordained to be |