is one which rests upon a plan in the form of the letter L a tee roof upon a plan in the form of the letter T; and an aitch roof upon a plan formed like the letter H; but when two common roofs, having their ridges parallel to each other, and a side of the one either joins one of the other, or these two sides intersect each other, and thereby leave a gutter above the roof; then the roof which is thus compounded of the two simple roofs is called an em roof, as the vertical section is in the form of the letter M: or rather an inverted W as M: this is an instance where the roof is denominated by the vertical section, and not by the plan. All roofs whatever are said to be truncated, whether they terminate in a plane or raised platform, or have a void at the top, bounded by a level curb.

When the side of a roof is a plane surface, except at the eaves, at which place it is concave, the roof is said to have a bell cast at that place.

The general names of the timbers are, straining pieces, tie pieces, and bearers; under straining pieces are included, principal rafters, camber beams, hip and valley rafters, collar beams, or straining beams, straining sills, struts, auxiliary rafters, or principal braces and studs.

Under the pieces are included, tie beams, diagonal ties, and truss posts; and under bearers are included. plates, purlins, common rafters, small rafters, ridge pieces, boarding and dragon beams.

The sloping sides of roofs are of two kinds, single and double, or plain and carcase: single roofs are those which have one row of rafters upon the same side; double or carcase roofs are those which have two ties of rafters; the lower tie supporting the upper by the intervention of transverse pieces called purlins.

Stone Bridges. A stone bridge is a thick wall built across a hollow, with one, two, three, or a series of apertures, formed into arcades, which either serve to lighten the masonry, or to give passage to a stream of water, or both.

When a stone bridge is resolved upon, the first consideration is its place in this several particulars should be taken into consideration, and the advantages compared to the disadvantages. As the height of the bridge depends on the banks of the river, the expense will be increased according to their height: therefore a convenient situation should be chosen, where the banks will be adequate in height to that necessary for the bridge, though the expense will be increased by the length of the bridge. In most cases, where the

river runs in a valley, a wide part of the stream must be preferred to a narrow part, as the water at this narrower part has not only a greater degree of velocity of itself, but the velocity would also be increased by the piers of the bridge; in times of heavy floods it would be liable to be thrown down, and in a navigable river the navigation would be impeded. As the expense depends on the bed of the river, it must also be taken into the account.

These being settled, the form and height of the arches come next under consideration; the height of the arches, which determine that of the bridge, depends on the rise of the water in time of floods; and whether there is to be a navigation, and what kind of vessels there are to pass.

Stone bridges ought to be constructed with as few arches as possible, which will not only give greater beauty, but will require fewer foundations, piers, and centerings, and also easier passage for craft. The piers ought to be so proportioned as to enable them to withstand the thrust of the adjacent arches, though the rest were thrown down. The number of arches ought to be odd, in order that one may stand in the middle, where the stream has its greatest velocity.

When the passage-way along the top of the bridge is a convex curve, the arches should diminish from the middle towards each extreme, so as to be similar to the middle one; this will allow a more free passage to the water, the velocity being greatest in the middle. With respect to the choice of arches, the elliptical, cycloidal, and equilibrated arches, are not only convenient, in allowing more room for the passage of ships at the hanches, but they require fewer materials than most other curves of the same dimensions.

When the extrados is convex, and the height of the arch small in proportion to the span, a segment of a circle may be used with success: in this case the arch should not exceed 60 degrees.

These particulars being fixed, the practice is as follows:-When the foundation of a stone bridge is to be laid in a river which is not very deep, a single or double inclosure of wood is formed, and the intervening space is rammed well with clay or chalk, to prevent the water from coming in. These inclosures are either made with piles driven closely together, and dovetailed at their jointings, or by piles driven at certain distances from one another, and grooved on the sides oppo

form the food was retained, and the body being duly supplied with nourishment, the stomach and rest of the system recovered their proper tone and energy. But the most extraordinary instance of bulimy, which perhaps ever occurred, is that recorded in the third volume of the "Medical and Physical Journal," communicated by Dr. Johnson, commissioner of sick and wounded seamen, to Dr. Blane, formerly physician to the navy. The subject was a Polish soldier, named Charles Domery, in the service of the French, on board of the Hoche frigate, which was captured by the squadron under the command of Sir John Borlase Warren, off Ireland, in 1799. He was 21 years of age, and stated that his father and brothers had been remarkable for their voracious appetites. He began when he was 13 years of age. He would devour raw and even live cats, rats, and dogs, besides bullock's liver, tallow candles, and the entrails of animals. One day (viz. September 7th, 1799) an experiment was made of how much this man could eat in one day. This experiment was made in the presence of the before-mentioned Dr. Johnson, Admiral Child, and Mr. Forster, agent for prisoners at Liverpool, and several other gentlemen. He had breakfasted at 4 o'clock in the morning on 4lbs. of raw cow's udder; at half past nine o'clock there were set before him 5lbs. of raw beef and 12 tallow candles of 1b. weight, together with 1 bottle of porter; these he finished by half past

ten o'clock; at one o'clock there were

put before him 5lbs. more of beef, 1lb. of candles, and three bottles of porter; he was then locked up in the room, and centries were placed at the windows, to prevent his throwing away any of his provi. sions. At two o'clock he had nearly finished the whole of the candles and great part of the beef; but without having had any evacuations by vomiting, stool, or urine. His skin was cool, pulse regular, and spirits good. At a quarter past six he had devoured the whole, and declared he could eat more; but the prisoners on the outside having told him that experiments were making upon him, he began to be alarmed.

BULK heads are partitions made athwart the ship with boards, by which one part is divided from the other; as the great cabin, gun-room, bread-room, and several other divisions. The bulk head afore is the partition between the forecastle and gratings in the head.

BULK breaking. See BREAKING.
BULL. See Bos.

BULL finch. See LoxIA.

BULL, among ecclesiastics, a written letter dispatched by order of the Pope, from the Roman chancery, and sealed with lead, being written on parchment, by which it is partly distinguished from a brief. See BRIEF.

BULL, golden, an edict or imperial constitution, made by the Emperor Charles IV. reputed to be the magna charta, or the fundamental law of the German empire.

It is called golden, because it has a golden seal, in the form of a pope's bull, tied with yellow and red cords of silk: upon one side is the Emperor represented sitting on his throne, and on the other the capital of Rome. It is also called Caroline, on Charles IV.'s account. Till the publication of the golden bull, the form and ceremony of the election of an emperor were dubious and undetermined, and the number of the electors not fixed.

This solemn edict regulated the functions, rights, privileges, and pre-eminen ces of the electors. The original, which is in Latin, on vellum. is preserved at Frankfort; this ordinance, containing thirty articles or chapters, was approved remains still in force. of by all the princes of the empire, and

BULLA, in natural history, a genus of insects of the Vermes Testacea. Animal a limax; shell univalve, convolute, unarmed with teeth; aperture a little straightened, oblong, longitudinal, very entire at the base; pillar oblique, smooth. There are nearly sixty species. B. lignaria is found on European coasts, and is about three inches long. The shell is thin, of a dirty colour, but within it is white. The inhabitants of this species, and, according to Gmelin, those of most of the genus, are furnished with an organ resembling the gizzard of a fowl, and which they appear to use for the purpose of masticating their food.

BULLET, an iron or leaden ball, or shot, wherewith fire-arms are loaded. Bullets are of various kinds; viz. red-hot bullets, made hot in a forge, intended to set fire to places where combustible matters are found. Hollow bullets, or shells made cylindrical, with an aperture and fuse at one end, which giving fire to the inside when in the ground, it bursts, and has the same effect with a mine. Chainbullets, which consist of two balls, joined by a chain three or four feet apart. Branch-bullets, two balls joined by a bar of iron, five or six inches apart. Twoheaded bullets, called also angles, twe

The diameter of a leaden bullet, weigh ing one pound, is 1.69 inches, according to Sir Jonas Moore; or, by a table in Muller's "Treatise of Artillery," 1.672 inches and the diameter of any other bullet is found by dividing 1.69 inches by the cube root of the number, which expresses how many of them make a pound; or by subtracting continually the third part of the logarithm of the number of bullets in the pound, from the logarithm .2278867 of 1.69, and the difference will be the logarithm of the diameter required. Thus the diameter of a bullet, of which 12 make a pound, will be found by subtracting 359:270, a third part of 1.0791812 the logarithm of 12, from the given logarithm .2278867; or because this logarithm is less than the former, an unit must be added, so as to have 1.2278867; and then the difference 8681597 will be the logarithm of the

diameter sought, which is .738 inches, observing that the number found will be always a decimal, because the number subtracted is greater than the other. We may also deduce the diameter of any bullet from its given weight, provided that the specific gravity of lead is known, for, since a cubic foot of lead weighs 11525 ounces, and 678 is to 355 as the cube of a foot, or 12 inches, i. e. 1728 to the content of a sphere, which is therefore 59.9.7 ounces: and since spheres are as the cubes of their diameters, the weight 59.9.7 is to 16 ounces, or one pound, as the cube 1728 is to the cube of the dameter of a sphere, which weighs sixteen ounces, or one pound; which cube is 4.66 63, and its root is 1.6706, the diameter sought.

By the rule above laid down is calculated the following table, shewing the diameters of leaden bullets, from 1 to 39 in the pound.

The upper horizontal column shews the number of bullets to a pound; the second their diameters; the third, the diameters of those of 10, 11, 12, &c. and the fourth those of 20, 21, 22, &c. and the last, those of 30, 31, 32, &c.

The government allows 11 bullets in the pound for the proof of muskets, and 14.5 in the pound, or 29 in two pounds, for service, 17 for the proof of carabines, and 20 for service; and 28 in the pound for proof of pistols, and 34 for service.

The diameter of musket bullets differs butth part from that of the musketbarrel; for if the shot but just rolls into the barrel, it is sufficient Cannon bullets or balls are of different diameters and weights, according to the nature of the piece.

BULLION, uncoined gold or silver in the mass.

Those metals are called so, either when smelted from the native ore, and not perVOL. III.

.512 0.507 0.5030 498

fectly refined; or when they are perfect, ly refined, but melted down in bars or ingots, or in any unwrought body, of any degree of fineness

When gold and silver are in their purity, they are so soft and flexible, that they cannot well be brought into any fash on for use, without being first reduced and hardened with an alloy of some other baser metal.

To prevent those abuses, which some might be tempted to commit in the making of such alloys, the legislators of civilized countries have ordained, that there shall be no more than a certain proportion of a baser metal to a particular quantity of pure gold or silver, in order to make them of the fineness of what is called the standard gold or silver of such a country.

According to the laws of England, all sorts of wrought plate in general ought to be made to the legal standard; and the

C

price of our standard gold and silver is the common rule whereby to set a value on their bullion, whether the same be in ingots, bars, dust, or in foreign specie; whence it is easy to conceive, that the value of bullion cannot be exactly known, without being first assayed, that the exact quantity of pure metal therein contained may be determined, and consequently whether it be above or below the standard.

Silver and gold, whether coined or uncoined (though used for a common measure of other things) are no less a commodity than wine, tobacco, or cloth; and may, in many cases, be exported as much to the national advantage as any other commodity.

BUMALDA, in botany, a genus of the Pentandria Digynia. Natural order of Dumosæ. Rhamni, Jussieu. Essential character: corolla five-petalled; styles villose capsule two-celled, two-beaked. There is but one species; viz. B. trifolia, with a shrubby stem; branches close, in all parts smooth; branches obscurely angular, jointed, purple; leaves opposite, petioled, ternate, pale underneath, on very short capillary petioles, spreading very much, or reflex; flowers terminating the branches in racemes, or capillary peduncles. Native of Japan.

BUMELIA, in botany, a genus of the Pentandria Monogynia class and order. Essential character: corolla five-cleft, with a five-leaved nectary; drupe oneseeded. There are seven species, all trees or shrubs, and natives of the WestIndies.

BUNIAS, in botany, a genus of the Tetradynamia Siliquosa. Natural order of Siliquosa. Crucifera, Jussieu. Essential character silicle deciduous, four-sided, muricated with unequal acuminate angles. There are nine species, of which B. cornuta, horned bunias, is a very singular plant. It has silicle transversely oval, finishing on each side in a horn, or very long and strong spine, so that the silicle resembles a pair of horns; in the middle of the silicle are four small spines, directed different ways. It is a native of the Levant and Siberia. B. spinosa, thorny bunias, is an annual plant, and a native of the South of France, Switzerland, Austria, and Italy.

BUNIUM, in botany, a genus of the Pentandria Digynia class and order. Natural order of Umbellatæ. Essential character: cor. uniform; umbel crowded; fruits ovate. There is but one species, viz. B. bulbocastanum, earth nut, or pig nut, has a perennial, tuberous root on

the outside, of a chesnut colour, within white, solid, putting forth slender fibres from the sides and bottom, of an agreeable sweetish taste, lying deep in the ground, commonly four or five inches deep, the stems from the surface tapering towards it, flexuose or bending to and from, and of a white colour; the universal involucre consists seldom of more than one, two, or three very slender leaves, but in most instances is altogether wanting; the partial umbel has sometimes twenty rays; the petals are lanceolate, entire, but rolled inwards, so as to appear as if they were emarginate; the filaments are longer than the petals; the pistils at first close, after divaricate, but never bend back. This description applies to the plant as usually found in Great Britain. That Brunium which is most common in many parts of the continent is somewhat different from ours; the segments of the leaf are not so fine, and nearer to parsly, whereas ours approach to fennel. The root is not so far within the ground, the leaves are larger and greener, and it sends forth leaves from the bulb itself. With us it grows on heaths, in pastures, woods, and among bushes, in a gravelly or sandy soil: it flowers in May and June.

BUNT, of a sail, the middle part of it; formed designedly into a bag or cavity, that the sail may gather more wind. It is used mostly in top sails, because courses are generally cut square, or with but small allowance for bunt or compass. The bunt holds much leeward wind, that is, it hangs much to leeward.

BUNT lines are small lines made fast to the bottom of the sails, in the middle part of the bolt rope, to a cringle, and so are reeved through a small block, seized to the yard. Their use is, to trice up the bunt of the sail, for the better furling it up.

BUNTING. See EMBERIZA.

BUOY, at sea, a short piece of wood, or a close-hooped barrel, fastened so as to float directly over the anchor, that the men who go in the boat to weigh the anchor may know where it lies.

Buor is also a piece of wood, or cork, sometimes an empty cask, well closed, swimming on the surface of the water, and fastened by a chain or cord to a large stone, piece of broken cannon, or the like, serving to mark the dangerous places near a coast, as rocks, shoals, wrecks of vessels, anchors, &c.

There are sometimes, instead of buoys, pieces of wood placed in form of masts, in conspicuous places; and sometimes large