Classification.-Bricks may be classified according to shape, density, methods of manufacture, position in kiln, color, and purpose. Arch brick usually means the partly or wholly vitrified product of the arches forming the fire-boxes of the kilns. A burnt brick is wholly vitrified. A compass brick is one shaped like a truncated wedge or voussoir. A capping or coping brick is one used for the upper courses of a wall or for a coping. Clinker, a brick from an arch of the clamp, so named from the sharp, glassy sound when struck. A feather-edged brick, one of prismatic form for arches, vaults, niches, etc. Fire-bricks are made of materials free from lime, magnesia, and potash, and from those metallic oxides which act as fluxes. Hollow bricks are such as contain open spaces for ventilation or warmth. Stocks, a name given by makers to various grades, as gray stock, red stock. Pecking, place, sandal, salmon, semel, etc., are local terms applied to imperfectly burned or refuse bricks. The expression air-brick denotes a grating let into the wall for ventilation.

must be allowed to cool very slowly; and especial care | brick is 2:4, giving for the weight of a solid foot 150 should be taken to lute up the doors of the fire-cham- pounds; that of common brick varies considerably, but bers and ash-pits, as well as any other openings that may be taken at 1894, or 118 pounds per foot; of firemay exist, since a current of cold air would injure, if brick the figures are 2201-137.6 pounds; of bricknot wholly destroy, the bricks with which it might work in cement, 18-1125 pounds, and in mortar the come in contact. same; of soft brick, 16-100 pounds per cubic foot. Brick absorbs from 1 to its weight of water. (L. M. H.). BRIDGEPORT, a city and seaport, one of the See Vol. IV. shire-towns of Fairfield co., Conn., on Long p. 253 Am. Island Sound, at the mouth of the Pequoned. (p. 284 nock River, which affords a good and comEdin. ed.). modious haven, somewhat encumbered at the entrance by a bar which has seldom over 14 feet of water. Lat. 41° 10' N., long. 73° 11′ W. It is on the New York and New Haven Railroad, at the junction of the Housatonic Railroad. The trains of the Naugatuck Railroad also run to Bridgeport. It has a regular passenger-steamboat service to New York. The city has very extensive and important manufactures of firearms, sewing-machines, cartridges, hardware, castings, axles, springs, locks, hats, machinery, carriages, and a great variety of other goods. Many of the streets are beautifully shaded, and the town has a large number of fine houses and churches, including places of worship for all the leading denominations. There are five national and three savings banks, three daily, one semi-weekly, and three weekly newspapers, systems of public and Catholic schools, a city high school, a training school, and a good library, a Catholic academy and convent; also the Golden Hill Academy and a ladies' seminary. Bridgeport has street railways, an opera-house, four public halls, two good hotels, and all of the conveniences of a large city. It is principally built on the west side of the river, that part which lies E. of the river being locally known as East Bridgeport. The city has important fishing and oystering interests. Population, in 1870, 18,969; in 1880, of the city, 27,643; of the township, 29,148. It ranks as the third city of the State in population, and the seventy-first in the United States. The city in 1880 contained 20,204 natives of the United States and 7439 foreigners; 443 persons were of African descent. There were 3735 dwellings, with an average of 74 persons to a dwelling. Bridgeport's history does not extend beyond 1821, when the town was organized, the city charter dating from 1836. Its recent growth has been extremely rapid.

Measuring-Brick-work is generally measured by the thousand bricks laid in the wall, but sometimes by the perch. There are various methods of estimating the number of bricks in any given work, and the conventionalities adopted in the several sections of the country are known as 'constructive measurements." The general practice is to allow a certain number of bricks to each square foot of wall-surface, the number varying with the thickness. The figures generally accepted are-for a 44-inch wall, 7 bricks per square foot; for a 9-inch wall, 14 bricks; for a 13-inch wall, 21 bricks; and so on in multiples of seven for each half brick added to the thickness. It is customary in brick walls to deduct all openings for doors, windows, arches, gateways, etc., but not for flues, ends of joists, trimmers, or girders, nor for the boxes of window-frames, nor any sills or lintels, account being taken of the extra labor in setting and the waste in laying.

To find the number of bricks required for a wall of given dimensions, allow one-tenth of the volume for mortar and deduct all apertures. Brick-work in tunnels and arches is usually measured by the cubic yard. It requires 38 bricks, 8×4×2, with joints from to inch wide, to lay one square yard if placed flat; if on edge it will take 73, and on end 149. Bricklaying, including mortar and scaffolding, will average for an entire dwelling $8 per M. The best pressed bricks in first-class work will cost from $15 to $20.

Sizes of Bricks.-In Cuba the moulds are said to be 11×5×2 inches; contents, 159 cubic inches; in South America, 123×6×2, or nearly 200 cubic inches. The British standard size, as fixed by law, is 8×4×23 inches, which gives a volume of 105 cubic inches. In the United States the sizes vary considerably, the average being about 84×4×23, containing 85 cubic inches, or twenty bricks to the cubic foot, whilst a cubic yard is assumed to contain 600 instead of 540, and a perch of 22 feet is reckoned as 500 bricks laid in the wall. In the Eastern States a common size is 8×6×2 inches (-98 cubic inches), which is less than the size of the Cuban brick. In some places 8×24×14 is not an unusual size; it contains only 384 cubic inches. Stock or place bricks commonly measure 8×4×24 inches, and weigh from 5 to 6 pounds each. Paving bricks should measure 9× 43 × 14 inches, and weigh from 4 to 4 pounds. Of this size 1 yard of paving requires 36 bricks laid flat, or 82 on edge. Of stock bricks 52 will be required if laid on edge. A good hand-moulded brick of 8×4×2 will weigh about 4 pounds, or 118 pounds per cubic foot, or 14223 tons per cubic yard, giving 500 to a ton. Machine-pressed bricks weigh about 5 pounds each. The specific gravity of pressed

VOL. I.-20

BRIDGEPORT, an incorporated village of Belmont co., Ohio, is on the Ohio River opposite Wheeling, W. Va. It is on the Cleveland and Pittsburg Railroad and the Cleveland, Tuscarawas Valley, and Wheeling Railroad. The Ohio River is here crossed by a suspension bridge, and there are three others over Wheeling Creek. Bridgeport has four hotels, a national bank, five churches, four schools, two flour-mills, two iron-mills, two glass-works, a stove-foundry, planing-mill, machineshop, and barrel-factory. There are three veins of coal underlying the adjoining country, and extensive coalworks are close to the town. It was settled in 1806 and incorporated in 1836, but has only begun to grow rapidly since 1870. Its property is valued at $850,000; its public debt is $4700, and its expenses for 1881 were $8000. Population, 2395.

BRIDGEPORT, a borough of Montgomery co., Pa., is pleasantly situated on the Schuylkill River opposite Norristown, 16 miles N. W. of Philadelphia. It is the eastern terminus of the Chester Valley Railroad, which connects here with the Philadelphia and Reading Railroad. It has two churches, two hotels, one foundry, three woollen-mills, two paper-mills, and gas-works. There are extensive lime-kilns in the vicinity. Two bridges across the Schuylkill connect this place with Norristown. It is surrounded by beautiful scenery. It was settled about 1760 and incorporated in 1851. Its property is valued at $700,000, and its public debt is $13,700. Many of the inhabitants are of Swedish descent. Population, 1802.

B

See

ed.).

BRIDGES.

RIDGES may be classified with reference to their in twelve years), St. Esprit, and Lyons, which are con

they may be of stone, wood, iron, of wood Vol. and iron (called "combination"), and of IV. P. 253 Am. ed. (p. steel. According to the second, they may 284 Edin. be classified as truss, arch, girder, suspension, tubular, pile, pontoon, draw, lift, swing, bowstring, etc. They are also designated by the relative position of the grade and other surface passed over as undergrade, overhead, through, halfthrough or low, and deck; or, with reference to the angle between the intersecting ways of communication, as right or askew. Bridges of special construction are sometimes designated by the name of their patentee, as the Burr, Town, Long, etc. The first method of classification is used in this article, as it conforms most closely with the history of bridges, and also enables us to illustrate the various subdivisions of the second method.

Until the last half century bridge-building was merely an art which its masters applied in conformity with their common sense, experience, and observation. The materials employed were those furnished by nature, as wood and stone wrought into proper shape, at great expense and with much labor, by hand tools, and put in place by the aid of heavy staging. No effort was made to compute the strength of the several parts of a bridge, but each constructor modelled his design and proportioned his details generally upon the precedents already established. The stone arch and the wooden truss were simply the result of intelligent observation and centuries of practice.

Squire Whipple (1847) and H. Haupt (1851) were the first American writers on the science of bridgeconstruction. Their methods and researches were conducted independently, and their results have furnished an invaluable basis for the great progress which has of late years been made both in the theory and practice of this branch of the profession.

In England the first purely theoretical writer on this subject was R. H. Bow (Nov., 1850), although data of a similar character had been published in the correspondence of Messrs. Stephenson, Fairbairn, Hodgkinson, and by Kirkaldy and Barlow, who contributed greatly to the development of iron bridgebuilding through their extensive experiments on the strength of materials in 1845 and subsequently.

Stone Bridges.-Stone bridges may be said to date from the period when man instinctively placed stepping stones in a stream, forming miniature piers in the shallow water. To trace the development of this class of bridges would necessitate an expansion far beyond our limits. We shall therefore merely refer to some of the most important structures of ancient and modern times, and especially since the introduction of railways.

The town of Alcantara ("the bridge"), in Spain, derives its name from the magnificent Roman bridge which there spans the Tagus. It was erected about A. D. 104, in honor of the emperor Trajan, of blocks of granite without cement, and consisted, until its partial destruction, of six arches of various spans. The total length was 670 feet, and height 210. The second arch on the right bank was blown up by the English in 1809, and its temporary substitute was again destroyed in 1836 to prevent the passage of the Carlist troops. At present only one arch, 40 feet high, remains.

It was the practice in some countries to bow the bridge, in plan, up stream, to resist the rush of floods more forcibly. Examples of such structures are found in the bridges of Avignon (one of which, having eighteen arches, was begun by St. Benezet in 1177, and finished

610

many places, making unequal angles, especially where the stream is strongest. Old London Bridge, which was begun in 1176 and required thirty-three years for completion, had nineteen arches and a great pier in the centre, intended for a steadying of the whole structure, instead of making an angle, as in the above-mentioned bridges.

Among ancient bridges mention is made of a bridge of a single arch in the city of Mostar, in Bosnia, much bolder than that of the Rialto in Venice. But these are both excelled by a bridge in China, built from one mountain to another, consisting of one single semicircular arch 400 cubits (600 feet) long and 500 cubits (750 feet) high, whence it is called the flying bridge.' "The stones which form the archivolt are from 7 to 12 feet in length. The voussoirs are intradossed and extradossed from a centre like unto the arches in Europe" (Thomas Pope's Treatise on Bridge Architecture, N. Y., 1811). Kircher also speaks of a bridge in the same country 360 perches long, without an arch, supported only by 300 pillars.

The next longest single span of which any record remains was the bridge of Trezzo, built about 1380 by order of Barnabo Visconti, duke of Milan. It was afterwards destroyed by Carmagnola. It consisted of a single arch of granite, very well constructed of stones in two courses; the innermost, 3 feet thick in the direction of the radius; the outermost, 9 inches. The span at low water was 251 feet, being the longest single-span arch on record, except that in China, of which no very authentic data remain. The rise at the crown from the surface of low water, which was also the position of the springing lines, was 87 feet 9-3 inches. The radius of the segment was 133 feet 0'5 inches. There remains about 24 feet of the arch near the haunches. It is supposed to have been surmounted by a crenellated balustrade terminating in two towers with battlements.

The Horseshoe Bend or Conemaugh Viaduct (fig. 1), built about 1833, is still standing, and is used by the Pennsylvania Railroad Company as a part of its main

FIG. 1.-Conemaugh Viaduct, Pennsylvania R. R. line. It is a substantial and imposing piece of masonry. about 75 feet high and with a semicircular arch of 80 feet span. The arch is 33 feet thick at the springing

FIG. 3.-Elsterthal Bridge, Saxon-Bavarian State Railway. Erie, and Western) Railroad, over the Starucca Creek, near its junction with the Susquehanna River. This bridge is 110 feet high and 1200 feet long. The eastern approach to the South Street Bridge,

Philadelphia (built 1872-73), presents some novel features in masonry arches worthy of notice. As the axis of the bridge is inclined to the centre-line of South Street at an angle of 33° 25', the change of direction

of the Philadelphia and Reading Railroad, Norristown | obliquely to the faces of its abutments. Formerly such branch. It is built of talcose slate, and consists of five bridges were generally built of masonry, and those porlarge, full-centre spans of 65 feet each, and four smaller tions of the arches at the acute angles were not resisted ones. The grade is 79 feet above the level of the creek. and upheld by a corresponding mass of masonry on the opposite side of the arch. This rendered a modification necessary in the bond or form of joints, leading to great difficulty in cutting them normal to the pressures, and also to a waste of material. The English, or Buck's, and the French systems of overcoming this difficulty are explained in the article on ARCH in ENCYCLOPEDIA BRITANNICA. A simpler method, however, exists, which can readily be executed by any ordinary mason. It consists in dividing the arch into a series of ring courses by planes passed parallel to the end-walls or "heads," and sliding these sections back until the proper angle of obliquity is obtained (fig. 6). Thus they will

PLAN

FIG. 5.-Eastern approach to South Street Bridge, Philadelphia, Pa.

The bridge is 492 feet long, 28 feet wide, and contains about 15,000 cubic yards of masonry. It was begun in May, 1881, and completed Dec. 1, 1882, at a cost of about $375,000.

Askew Bridges.-It frequently happens that two lines of communication do not intersect at right angles, in which case the bridge crossing one of them is placed

FIG. 6.-Askew Arch on Philadelphia and Reading R. R. have the same span and rise, but the bond is less perfect in consequence of the interior soffit being broken, as it were, into steps. As, however, each segment is a right arch, and the pressure is normal to the joints and bearings, the advantages are so great that appearance is sacrificed for utility, safety, and economy.

The only instance believed to exist in America of an askew arch with helicoidal joints, as described by Mr. Buck, is that on the Lebanon Valley (now Philadelphia and Reading) Railroad over Sixth Street in Reading, Pa.

It was built in 1856-58 by Richard B. Osborn, C. E., under great difficulties, as it was almost impossible to secure masons who could prepare the templates and apply them to the joints. This form of arch is clearly illustrated in fig. 7.

The present practice for oblique crossings is to use some form of wooden or iron truss, supported, when possible, upon iron columns and abutments.

The masonry bridge crossing the Schuylkill River on the Philadelphia and Reading Railroad at the Falls of Schuylkill is an example of an askew arch built of segments of circles, as shown in fig. 6. In this bridge there are six arches, each having a span of 83 feet and a rise of 26 feet. The exterior walls are of rock-faced ashlar. There are eight segments in the length of each arch, so "stepped off" in plan that the front edges are

on a line, making, with the head-walls, an angle of 21° 30', which is the angle of the stream with the line of the bridge. It was built about 1854 by J. Dutton Steel, C. E.

WOODEN BRIDGES.

One of the most striking instances of the early application of science to the construction of wooden bridges was that of the famous structure spanning the Rhine at Schaffhausen, erected by Ulric Grubenmann, a common carpenter of Teuffen, in 1758. This bridge, 364 feet long and 18 wide, was destroyed by the French in April, 1799. But this structure, with its two spans,, was surpassed in boldness by the one over the Limmat at Wettingen, near Baden, which had a clear span of 368 feet. It was built by the same Ulric Grubenmann,