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Bridge.

1. (Engineering.) A structure erected over a water-way, ravine, or road, for the transit of persons, animals, or vehicles. A viaduct.

The only reference to a bridge in the canonical Scriptures is an indirect one, in a name referring to the “bridge of the sons of Jacob.” It is at a place northeast of the Sea of Galilee, and a bridge still exists at the place.

The bridge erected by Nitocris, across the Euphrates at Babylon, consisted of stone piers supporting a series of wooden platforms, which were capable of being withdrawn, to prevent passage at night between the portion of the city on the respective sides of the river. (Herodotus, 1. 186.)

The “huge stones cramped together by iron bars and melted lead” were probably in the piers. We may surmise that the foundations of these were laid while the river was temporarily diverted, or made in an artificial channel to which the river was subsequently transferred. Either plan was possible in that country, and the former was tried, to the cost of the Babylonians, by Cyrus, many centuries after Nitocris.

Ancient bridges of great magnitude exist in China. This ingenious people constructed them of wood, stone, chains, and ropes, before history commenced to be written in Europe. The great wall of China (Wan-li-chang, the myriad-mile-wall) was finished about 220 B. C., and has many stone bridges over the various streams which it crosses in its course of 1,250 miles. It puts into the shade the British wall of Agricola, which united the Tyne and the Solway, 80 miles; and the other Roman wall which united the Forth and Clyde, 36 miles.

The Egyptians built no permanent bridges across the Nile, but were familiar with framing trestlework, and with ponton and draw bridges; the latter are seen frequently in their paintings representing fortified towns, sieges, etc.

The Greeks had but small rivers, and had no stone bridges until after the Roman conquest.

We learn from the Greek historians that bridges were constructed by Cyrus (536 B. C.), Darius (490 B. C.), Xerxes (480 B. C.), and Pyrrhus (280 B. C.). Each of these was a military bridge for a special purpose, and had no permanent character. The bridge of Cyrus, over the Meander, was supported on boats, like those which crossed the Bosphorus and the Hellespont under the orders of his successors; Xenophon states that the bridge of Cyrus had seven boats.

The bridge of Xerxes was 500 paces in length. Ships were used as pontons; cords of flax and biblos united them; transverse beams were laid on the ropes; planks on the beams; soil on the planks; and the armies crossed thereon. Cords and posts at the sides afforded some degree of protection.

How many bridges were built by Pyrrhus in his expeditions, history does not inform us; but the bridges in his Italian campaigns, about 280 B. C., over the streams emptying into the Adriatic, are mentioned by the Greek historians.

The first bridge in Rome was built across the Tiber, 621 B. C., by Ancus Martius, uniting the Janiculum and Mons Aventinus, and was memorable for its defence by Horatius Cocles against Lars Porsenna the Etruscan, about 508 B. C.; also as the spot whence the body of Heliogabalus was cast into the Tiber, a stone about his neck, about A. D. 218. It was called the Pons Sublicius, from its having been built upon stakes, or piles. The original bridge was built about the time of Josiah, king of Judah, and a few years previous to Nebuchadnezzar.

The Pontus Salarius was erected by Tarquinius Priscus, about 600 B. C. It spanned the Teverone, and is believed to have had three arches of stone. Doubts have been suggested as to the authenticity of this account; but it is not surprising when we consider the Cloaca Maxima, constructed in the same reign.

The Romans appear to have been the first to construct arched bridges; several of which still exist in Syria and Palestine, and are the oldest stone-arch bridges in existence, unless some of the Etruscan and Chinese bridges antedate them.

The Pons Senatorius was erected across the Tiber by Caius Flavius Scipio, 127 B. C.

Julius Caesar's and Trajan's bridges.

A trestle-bridge on piles (a. Fig. 924) was built by Julius Caesar across the Rhine about 55 B. C. He left an account of its construction, but the authorities construct it differently from the specification extant. It was founded upon piles driven into the bed of the river. The piles were united by a beam, on which were laid joists in the direction of the length of the bridge. Upon the joists were laid hurdles supporting the road-bed. An inclined fender protected the piers up stream, and each pier was stayed below by a cluster of piles. It was built in ten days.

A magnificent bridge with four stone arches was built by Augustus near Narni, on the road from Rome to Loretto. The arches were respectively 75, 135, 114, and 142 feet span. One arch remains.

The bridge of Trajan (b, Fig. 924), which crossed the Danube, was one of the greatest engineering works of antiquity. It was constructed of timber resting upon stone piers. Each span consisted of three rows of concentric arches, united by bindingpieces formed upon each division; these abutted upon timbers radiating with the curve, which were framed into heads and sills, again strengthened by braces and struts; the joists which carried the floor traversed the bridge, and rested upon strong plates laid upon the timber arches.

Apollodorus was the architect, A. D. 105. The bridge was 4,770 feet long. The foundation was made by sinking large barges filled with stones, lime, and sand, and filling in the interstices with [380] bags of similar material. On these the piers were built. The bridge had 20 semicircular arches of 180 feet 5 inches span. Their springings were 46 feet above the general level of the river. The piers were 150 feet high above their foundations, 64 feet thick, 85 feet 3 inches wide. The bridge was 60 feet wide.

It was destroyed by Hadrian, the successor of Trajan, to prevent the incursions of the barbarians. Rome was then beginning to assume the defensive.

Among the other Roman bridges which yet remain, whole or in part, to testify to the skill of the engineers and extort our admiration, are those of Merida and Alcantara, in Spain. The former is over the Guadiana, 3,900 feet long, and has 64 arches. The latter is over the Tagus, 670 Spanish feet long, 6 arches; road-bed 205 feet above the river.

The bridges of London are celebrated in history, especially that portion of history in which we who speak English are most interested. A wooden bridge existed over the Thames in A. D. 978. One was built of wood in 1014; one by Peter of Colechurch, 1176-1200, with houses on each side connected by arches of timber which crossed the street. This was burned in July, 1212, and 3,000 persons perished. The buildings being on fire at the Surry end, a great crowd rushed to see the fire, and the wind blew the burning shingles to the north end, lighting the buildings at the Middlesex side of the river. Between fire and water the loss of life was dreadful. The bridge was restored in 1300; again partially burned in 1471, 1632, and 1725. The houses were pulled down in 1756. At what time stone arches were substituted for wooden spans does not appear. When the present London bridge was built in 1831, the elm piles of the old bridge were yet sound, after 600 years use.

In the twelfth and thirteenth centuries A. D. a very useful society flourished in Europe, called the “Brothers of the bridge.” The building of bridges was at that time deemed an act of piety, and we must highly respect that devotion which, in the fear of God, finds its expression in deeds of exalted usefulness.

Benezet built a bridge at Avignon over the Rhone, which was finished in 1188. It had 18 stone arches, and was 3,000 feet long. The arch which supported the chapel dedicated to St. Nicholas, the patron of sailors and those whose business is upon the waters, remained long after the other arches had been swept away by the storms of centuries. Benezet's tomb was in the crypt.

About 1300, Issim, the Moorish king of Granada, erected a fine bridge at Cordova, across the Guadalquiver.

Perronet mentions a stone bridge of three arches, one of which had a span of 159 feet 9 inches, at Verona, erected in 1354. Also a bridge with a stone arch 183.8 feet span, 70.6 feet rise, erected 1454, at Vielle Bronde, over the Altier, by Grennier.

The Rialto, of Venice, was erected by Antonio del Ponte, 1588. It has a span of 98 1/2 feet.

The art of bridge-building, which was understood by the Romans, fell into disuse when that political system became disintegrated. When the arts revived, the Italians took the lead.

Much has been done of late years, and the designs become more and more bold. London Bridge, Menai Tubular Bridge, the St. Lawrence Bridge at Montreal, the Cincinnati Bridge, Southwark Bridge, London, the Cabin John Creek Bridge, Maryland, and the Schuylkill Bridge at Philadelphia, are trophies of their kind. The suspension bridge across the East River, New York (see Frontispiece), is by far the boldest undertaking in the suspension line, nearly 600 feet greater than the now widest span, — the bridge at Cincinnati. The steel tubular-arch bridge at St. Louis is to cross the Mississippi in three spans, which have only one rival among arches, — a single-span bridge in Holland.

The highest bridge in the world is the Verrugas Viaduct on the Lima and Oroya Railroad, in the Andes of Peru. It crosses a mountain-torrent called the Agua de Verrugas, in a wild and picturesque locality 12,000 feet above the level of the sea. The structure consists of four deck-spans, or trusses, three of which are 110 feet long, and one, the central span, 125 feet long. The spans rest on piers built of wrought-iron columns. The piers are 50 feet long by 15 feet wide on top. There being three piers, the total length of the viaduct is 575 feet. The piers are respectively 145 feet, 252 feet, and 187 feet high. Each pier consists of 12 legs, which in plan form a rectangle. The legs are composed of a series of wrought-iron six-segment columns, in lengths of 25 feet, connections being made by cast-iron joint-boxes having tenons on each end running into the column. The columns have an exterior diameter, including flanges, of 16 inches.

The mountain-chain will be crossed at an altitude of 15,000 feet by a tunnel 3,000 feet in length. The grades are the steepest known on any ordinary railway. The workmen employed are Cholos Indians, the only operatives who can endure for a prolonged period the rarified atmosphere at this great elevation.

The subject, after this slight historical general sketch, will be considered under the headings which naturally suggest themselves, founded upon the differences in material, construction, and purpose.

See under their respective heads: —

Arched-beam bridge.Lattice-bridge.
Balance-bridge.Leaf-bridge.
Bascule-bridge.Lifting-bridge.
Boat-bridge.Military-bridge.
Bowstring-bridge.Millstone-bridge.
Bridge-equipage.Pile-bridge.
Bridge-stone.Pivot-bridge.
Bridge-train.Platform-bridge.
Cable-suspension bridge.Ponton-bridge.
Canal-bridge.Raft-bridge.
Carriage-bridge.Rolling-bridge.
Chain-bridge.Rope-bridge.
Check-bridge.Skew-bridge.
Chinka-bridge.Steel-bridge.
Counterpoise-bridge.Stiffening-girder.
Drawbridge.Stone-bridge.
Electric bridge.Suspension-bridge.
Ferry-bridge.Swing-bridge.
Fire-bridge.Swivel-bridge.
Flame-bridge.Tension-bridge.
Floating-bridge.Trainway for ferry-boats.
Flying-bridge.Trestle-bridge.
Foot-bridge.Truss-bridge.
Furnace-bridge.Tubular-bridge.
Girder-bridge.Tubular-arch bridge.
Half-lattice girder.Turn-bridge.
Hoist-bridge.Viaduct.
Hose-bridge.Weigh-bridge.
Iron bridge.Wooden bridge.
Iron-arch bridge.

2. (Steam.) a. A lower vertical partition at the back of the grate-space of a furnace. The flame in passing the bridge is deflected upward against the bottom of the boiler.

Bridges are of metal or fire-brick. They may be hollow and form a part of the water-space of the boiler. Such are called water-bridges. [381]

When a hollow water-bridge depends from the bottom of the boiler of which it forms a part, it is called a hanging bridge.

A bridge in the mid-space, with flue-space above and below it, is a mid-feather.

b. “The middle part of the fire-bars in a marine boiler, on either side of which the fires are banked.” — Admiral Smyth.

3. (Shipbuilding.) A partial deck extending from side to side of a vessel amidships. It is common in steam-vessels, affording a convenient station for the officer in command, and extends over the space between the paddle-boxes. It is also known in England as the hurricane-deck or bridge-deck.

4. a. (Metallurgy.) The low wall of division between the fuel-chamber and hearth of a reverberatory furnace (which see).

b. (Puddling.) The wall at the end of the hearth towards the stack, compelling the caloric current to ascend and then descend towards the foot of the stack.

5. (Music.) A bar placed beneath the strings of a musical instrument to elevate them above the sounding-board.

6. (Ordnance.) The pieces of timber between the transoms of a gun-carriage. （English.)

7. (Horology.) A piece raised in the middle and fastened at both ends to the watch-plate, and forming a bearing for one or more pivots.

When supported at one end, it is a cock.

8. (Engraving.) A board resting on end-cleats, used by an engraver to span the plate on which he is working, to support the hand clear of the plate.

9. (Mining.) The platform or staging by which ore, limestone, fuel, etc., are conveyed to the mouth of a smelting-furnace.

10. (Electricity.) A device used for measuring the resistance of an element of an electric circuit. See electric bridge.

1877.

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