a work of masonry or timber, consisting of one or more arches built over a river, canal, or the like, for the conveniency of passing the same. See ARCHITECTURE, n°122; and CANAL.
The first inventor of bridges, as well as of ships and crowns, is by some learned men supposed to be Janus: their reason is, that on several ancient Greek, Sicilian, and Italian coins, there are represented on one side a Janus, with two faces; and on the other a bridge, or a crown or a ship.
Bridges are a sort of edifices very difficult to execute on account of the inconvenience of laying foundations and walling under water. The earliest rules and instructions relating to the building of bridges are given by Leon Battista Alberti, Architect. I. viii. Others were afterwards laid down by Palladio, I. iii. Serlio, I. iii. c. 4. and Scammozzi, I. v. all of which are collected by M. Blondel, Cours d'Archit. p. 629, seq. The best of them are also given by Goldman, Baukunst, I. iv. c. 4. p. 134, and Hawksmoor's History of London bridge, p. 26, seq. M. Gautier has a piece express on bridges, ancient and modern; Trait des Ponts, Paris 1716, 12mo.
The parts of a bridge are, The piers; the arches; the pavement, or way over for cattle and carriages; the foot-way on each side, for foot-passengers; the rail or parapet, which incloses the whole; and the buttments or ends of the bridge on the bank.
The conditions required in a bridge are, That it be well-designed, commodious, durable, and suitably decorated. The piers of stone-bridges should be equal in number, that there may be one arch in the middle, where commonly the current is strongest; their thickness is not to be less than a sixth part of the span of the arch, nor more than a fourth; they are commonly guarded in the front with angular flerlings, to break the force of the current; the strongest arches are those whose sweep is a whole semicircle; as the piers of bridges always diminish the bed of a river, in case of inundations, the bed must be sunk or hollowed in proportion to the space taken up by the piers, as the waters gain in depth what they lose in breadth, which otherwise conduce to wash away the foundation and endanger the piers: to prevent this, they sometimes diminish the current, either by lengthening its course, or by making it more winding; or by stopping the bottom with rows of planks, flakes, or piles, which break the current.
Among the Romans, the building and repairing of bridges was first committed to the pontifices or priests; then to the censors, or curators of the roads; lastly, the emperors took the care of bridges into their own hands. Thus Antoninus Pius built the Pons Janiculanus of marble; Gordian restored the Pons Cestius; and Adrian built a new one denominated from him. In the middle-age, bridge-building was reckoned among the acts of religion; and a regular order of Hospitallers was founded by St Benoet, towards the end of the 12th century, under the denomination of pontifices, or bridge-builders, whose office it was to be assistant to travellers, by making bridges, settling ferries, and receiving strangers in hospitals, or houles built on the banks of rivers. We read of one hospital of this kind at Avignon, where the hospitallers dwelt under the direction of their first superior St Benoet. The Jesuit Raynaldus has a treatise express on St John the bridge-builder.
Among the bridges of antiquity, that built by Trajan over the Danube is allowed to be the most magnificent.
Among modern bridges, that of Westminster, built over the river Thames, may be accounted one of the finest in the world: it is 44 feet wide, a commodious foot-way being allowed for passengers, on each side, of about seven feet broad, raised above the road allowed for carriages, and paved with broad moor-stones, while the space left between them is sufficient to admit three carriages and two horses to go abreast, without any danger. Its extent from wharf to wharf is 1220 or 1223 feet, being full 300 feet longer than London-bridge. The free water-way under the arches of this bridge is 870 feet, being four times as much as the free water-way left between the flerlings of London bridge; this disposition, together with the gentleness of the stream, are the chief reasons why no sensible fall of water can ever stop, or in the least endanger, the smallest boats in their passage through the arches.
It consists of 13 large and 2 small arches, together with 14 intermediate piers.
Each pier terminates with a salient right angle against either stream: the two middle piers are each 17 feet in thickness at the springing of the arches, and contain 3000 cubic feet, or near 200 tons, of solid stone; and the others decrease in width equally on each side by one foot.
All the arches of this bridge are semicircular; they all spring from about two feet above low-water mark; the middle arch is 76-feet wide, and the others decrease in breadth equally on each side by 4 feet.
This bridge is built of the best materials; and the size and disposition of these materials are such, that there is no false bearing, or so much as a false joint in the whole structure; besides that it is built in a neat and elegant taste, and with such simplicity and grandeur, that, whether viewed from the water, or by the passengers who walk over it, it fills the mind with an agreeable surprize. The semi-rectangular towers which form the recesses of the foot-way, the manner of placing the lamps, and the height of the balustrade, are at once the most beautiful, and, in every other respect, the best contrived. London-bridge consists of 20 locks or arches, 19 of which are open, and one filled up or obscured. It is 900 feet long, 60 high, and 74 broad, with almost 25 feet aperture in each arch. It is supported by 18 piers, from 25 to 34 feet thick; so that the greatest water-way when the tide is above the sterlings is 450 feet, scarce half the width of the river; and below the sterlings, the water-way is reduced to 194 feet. Thus a river 900 feet wide is here forced through a channel of 194 feet.
London bridge was first built of timber, some time before the year 994, by a college of priests, to whom the profits of the ferry of St Mary Overy's had descended; it was repaired, or rather new built of timber, in 1163. The stone bridge was begun by king Henry in 1176, and finished by king John in 1200.
The architect was Peter of Colechurch, a priest. For the keeping it in repair, a large house is allotted, with a great number of offices, and a vast revenue in land, &c. The chief officers are two bridge-masters, chosen yearly out of the body of the livery. The defects of this bridge are the narrowness and irregularity of the arches, and the largeness of the piers, which, together with the sterlings, turn the current of the Thames into many frightful cataracts, which must obstruct and endanger the navigation through the bridge. The sterlings have been added, to hinder the piers from being undermined by the rotting of the piles on which they are built; for by means of these sterlings the piles are kept constantly wet; and thus the timber is kept from decaying, which always happens when it is suffered to be alternately wet and dry.
Blackfriars bridge, situated near the centre of the city, and built according to a plan drawn by Mr Robert Mylne, is an exceeding light and elegant structure. The arches are only 9 in number; but very large, and of an elliptical form. The centre-arch is 100 feet wide; those on the sides decrease in a regular gradation; and the width of that near the abutment at each end is 70 feet. It has an open balustrade at the top, and a foot-way on each side, with room for three carriages abreast in the middle. It has also recesses on the sides for the foot-passengers, each supported by two lofty Ionic columns.
The longest bridge in England is that over the Trent at Burton, built by Bernard abbot of Burton, in the 12th century; it is all of squared free stone, strong and lofty, 1545 feet in length, and consisting of 34 arches. Yet this comes far short of the wooden bridge over the Drave, which according to Dr Brown is at least five miles long.
But the most singular bridge in Europe is that built over the river Tawe in Glamorganshire. It consists of one stupendous arch, the diameter of which is 175 feet, the chord 140, the altitude 35, and the abutments 32. This magnificent arch was built by William Edward, a poor country man, in the year 1756.
The famous bridge of Venice, called the Rialto, consists of but a single arch, and that a flat or low one, and passed for a masterpiece of art. It was built in 1591, on the design of Michael Angelo; the span of the arch is 98½ feet, and its height above the water only 23. Poulet mentions a bridge of a single arch in the city of Munster in Bothnia, much bolder than that of the Rialto at Venice. But these are nothing to a bridge in China, built from one mountain to another, consisting of a single arch 400 cubits long and 500 in height, whence it is called the flying-bridge: a figure of it is given in the Philosophical Transactions. Kircher also speaks of a bridge in the same country 360 perches long, supported by 300 pillars.
Ruben Bridge, Pont de jone, is made of large sheaves of rushes growing in marshy grounds, which they cover with boards or planks; they serve for crossing ground that is boggy, miry, or rotten. The Romans had also a sort of subterranean bridges made by the folder, of boats, or sometimes of casks, leathern bottles, or bags, or even of bullocks bladders blown up and fastened together, called ofogafri. M. Couplet gives the figure of a portable bridge 200 feet long, easily taken asunder and put together again, and which 40 men may carry. Frezier speaks of a wonderful kind of bridge at Apurima in Lima, made of ropes, formed of the bark of a tree.
Pendent or Hanging Bridges, called also Philosophical Bridges, are those not supported either by posts or pillars, but hung at large in the air, only supported at the two ends or buttends. Instances of such bridges are given by Palladio and others. Dr Wallis gives the design of a timber-bridge 70 feet long, without any pillars, which may be useful in some places where pillars cannot be conveniently erected. Dr Plot affirms us, that there was formerly a large bridge over the castle-ditch at Tutbury in Staffordshire, made of pieces of timber, none much above a yard long, and yet not supported underneath either with pillars or archwork, or any sort of prop whatever.
Drawn-Bridge, one that is fastened with hinges at one end only, so that the other may be drawn up; in which case, the bridge stands upright, to hinder the passage of a ditch or moat.
Flying-Bridge, or Pons ductorius, an appellation given to a bridge made of pontoons, leather boats, hollow beams, casks, or the like, laid on a river, and covered with planks, for the passage of an army.
Flying-Bridge (pont volant) more particularly denotes a bridge composed of one or two boats joined together by a sort of flooring, and surrounded with a rail or balustrade; having also one or more masts, to which is fastened a cable, supported, at proper distances, by boats, and extended to an anchor, to which the other end is fastened, in the middle of the water: by which contrivance, the bridge becomes moveable, like a pendulum from one side of the river to the other, without any other help than the rudder.—Such bridges sometimes also consist of two stories, for the quicker passage of a great number of men, or that both infantry and cavalry may pass at the same time.
In Plate CVIII. is represented a flying-bridge of this kind. Fig. 2. is a perspective view of the course of a river and its two banks. a, b, c, d, Two long boats or batteaux, which support the flying-bridge. G, H, K, L, two masts joined at their tops by two transverse pieces, or beams, and a central arch, and supported in a vertical position by two pair of shrouds and two chains L, N, H, R. M, a horse, or cross piece, over which the rope or cable M, F, e, f, that rides or holds the bridge against the current, passes. E, a roll or windlass round which... Bridge, which the rope M, F, e, f, is wound. a, b, The rud- ders. A.B, and C.D, two portions of bridges of boats fastened to the bank on each side, and between which the flying-bridge moves in passing from one side of the river to the other. e, f, Chains supported by two punts, or small flat-bottomed boats; there are five or six of these punts at about 40 fathoms from one another. The first, or farthest from the bridge, is moored with an- chors in the middle of the bed of the river.
Fig. 3. Is a plan of the same bridge. a, b, c, d, The two boats that support it. K and G, the two masts. KFG, the transverse piece or beam over which the cable passes. E, the roll, or windlass, round which the rope or cable is wound. a, b, The rudders. O, a boat. e, One of the punts, or small flat-bottomed boats that support the chain. N, N, pumps for extracting the wa- ter out of the boats. P, P, captains.
Fig. 4. Lateral elevation of the bridge. a, c, One of the boats. b, The rudder. E, The roll, or wind- lass. M, The horse, or cross-piece. GH, One of the masts. E, M, H, F, The cable. In this view the ba- lustrade running along the side of the bridge is plainly exhibited.
Fig. 5. Elevation of the hinder or stern part of the bridge. a, b, The two boats. GH, KL, The two masts. HL, The upper transverse beam. p, q, The lower transverse beam, or that over which the cable passes, and on which it slides from one mast to the o- ther; this beam is therefore always kept well greased. p, k, g, g, Shrouds extending from the sides of the bridge to the tops of the masts. M, The horse or cross-piece over which the cable passes to the roll or windlass E.
BRIDGES OF BOATS are either made of copper or wooden boats, fastened with stakes or anchors, and laid over with planks. One of the most notable exploits of Julius Caesar was the expeditious making a bridge of boats over the Rhine. Modern armies carry cop- per or tin boats, called pontoon, to be in readiness for making bridges; several of these being joined side by side till they reach across the river, and planks laid over them, make a place for the men to march on. There are fine bridges of boats at Beaucaire and Rouen, which rise and fall with the water; and that at Seville is said to exceed them both. The bridge of boats at Rouen, built in lieu of the flatly stone-bridge erected there by the Romans, is represented by a modern writ- er as the wonder of the present age. It always floats, and rises and falls with the tide, or as the land-waters fill the river. It is near 300 yards long, and is paved with stone, just as the streets are; carriages with the greatest burdens go over it with ease, and men and horses with safety, though there are no rails on either hand. The boats are very firm, and well moored with strong chains, and the whole well looked after and con- stantly repaired, though now very old.
BRIDGE OF COMMUNICATION, is that made over a river, by which two armies, or forts, which are separated by that river, have a free communication with one ano- ther.
FLOATING-BRIDGE, is ordinarily made of two small bridges, laid one over the other, in such manner as that the uppermost stretches and runs out, by the help of certain cords running through pulleys placed along the sides of the under-bridge, which push it forwards till the end of it joins the place it is designed to be fixed on. When these two bridges are stretched out to their full length, so that the two middle ends meet, they are not to be above four or five fathoms long; because, if longer, they will break. Their chief use is for surprising out-works, or posts that have but nar- row moats. In the memoirs of the royal academy of sciences we find an ingenious contrivance of a float- ing-bridge, which lays itself on the other side of the river.
Natural, implies a bridge not constructed by art, but the result of some operation of nature.
A most wonderful work of this kind is described by Mr Jefferson in his State of Virginia. It is on the ascent of a hill, which seems to have been cloven through its length by some great convulsion. The fis- sure, just at the bridge, is, by some measurements, 270 feet deep, by others only 205. It is about 45 feet wide at the bottom, and 90 feet at the top; this of course determines the length of the bridge, and its height from the water. Its breadth in the middle is about 60 feet, but more at the ends, and the thickness of the masts at the summit of the arch about 40 feet. A part of this thickness is constituted by a coat of earth, which gives growth to many large trees. The refuse, with the hill on both sides, is one solid rock of limestone. The arch approaches the semi-elliptical form; but the larger axis of the ellipse, which would be the cord of the arch, is many times longer than the transverse. Though the sides of this bridge are provided in some parts with a parapet of fixed rocks, yet few men have resolution to walk to them and look over into the abyss. You involuntarily fall on your hands and feet, creep to the parapet, and peep over it. Looking down from this height about a mi- nute, gave our author a violent headache. If the view from the top be painful and intolerable, that from be- low is delightful in an equal extreme. It is impossible for the emotions arising from the sublime to be felt beyond what they are here: so beautiful an arch, so elevated, so light, and springing as it were up to hea- ven, the rapture of the spectator is really indefinable! The fissure continuing narrow, deep, and straight for a considerable distance above and below the bridge, opens a short but very pleasing view of the North- mountain on one side and Blue-ridge on the other, at the distance each of them of about five miles. This bridge is in the county of Rockbridge, to which it has given name, and affords a public and commodious pallage over a valley, which cannot be crossed elsewhere for a considerable distance. The stream passing under it is called Cedar-creek. It is a water of James River, and sufficient in the driest seasons to turn a grist-mill, though its fountain is not more than two miles above.
Don Ulloa mentions a break, similar to this, in the province of Angaraez, in South America. It is from 16 to 22 feet wide, 111 feet deep, and of 1.3 miles continuance, English measures. Its breadth at top is not sensibly greater than at bottom. Don Ulloa in- clines to the opinion, that this channel has been effect- ed by the wearing of the water which runs through it, rather than that the mountain should have been broken open by any convulsion of nature. But if it had been worn by the running of water, would not the rocks which form the sides have been worn plane? or if, meeting in some parts with veins of harder stone, Bridge. the water had left prominences on the one side, would not the same cause have sometimes, or perhaps generally, occasioned prominences on the other side also? Yet Don Ulloa tells us, that on the other side there are always corresponding cavities, and that these tally with the prominences so perfectly, that, were the two sides to come together, they would fit in all their indentures, without leaving any void. In fact, this does not resemble the effect of running water, but looks rather as if the two sides had parted asunder. The sides of the break, over which is the Natural bridge of Virginia, consisting of a veiny rock which yields to time, the correspondence between the salient and re-entering inequalities, if it existed at all, has now disappeared. This break has the advantage of the one described by Don Ulloa in its finest circumstance; no portion in that instance having held together, during the separation of the other parts, so as to form a bridge over the abyss.
gunnery, the two pieces of timber which go between the two transoms of a gun-carriage, on which the bed rests.
music, a term for that part of a stringed instrument over which the strings are stretched. The bridge of a violin is about one inch and a quarter high, and near an inch and a half long.
Bridge Town, the capital of the island of Barbadoes, situated in W. Long. 61° N. Lat. 13°. It stands in the most part of Carlisle bay. This originally was a most unhealthy situation, and was chosen entirely for its convenience for trade; but is now deemed to be as healthy as any place in the island. The town itself would make a figure in any European kingdom. It is said to contain 1500 houses, and some contend that it is the finest the British possess in America. The houses in general are well built and finished, and their rents as high as such houses would let for in London. The wharfs and quays are well defended from the sea, and very convenient. The harbour is secure from the north-east wind, which is the constant trade wind there; and Carlisle-bay is capable of containing 500 ships, and is formed by Needham and Pelican points. But what renders Bridge-town the finest and most desirable town in the West Indies is its security against any attacks from foreign enemies. It is defended on the westward by James-fort, which mounts 18 guns. Near this is Willoughby’s fort, which is built upon a tongue of land running into the sea, and mounts 12 guns. Needham’s fort has three batteries, and is mounted with 20 guns; and St Anne’s fort, which is the strongest in the island, stands more within land. In short, according to Mr Douglas, there is all along the lee-shore a breastwork and trench, in which, at proper places, were 29 forts and batteries, having 308 cannon mounted, while the windward shore is secured by high rocks, steep cliffs, and foul ground. Such was the state of the fortifications in 1717; but since that time they have been much strengthened. Bridge-town is destitute of few elegancies or conveniences of life that any city of Europe can afford. The church of St Michael exceeds many English cathedrals in beauty, largeness, and convenience; and has a fine organ, bells, and clock. Here also is a free-school for the instruction of poor boys, an hospital, and a college. The latter was erected by the society for propagating the Christian religion, in pursuance of the will of Colonel Christopher Codrington, who left about L2000 a-year for its endowment, for maintaining professors and scholars to study and practise divinity, surgery, and physic. See Codrington.