the abutment and pier are therefore placed at an angle of 50° with the longitudinal direction of the girders, which are two in number, and of uniform depth throughout, between which the double line of railway is carried. This elegant specimen of wrought ironwork was designed and executed by Mr. W. Fair bairn, whose name is so honourably connected with the Britannia and Conway Tubular Bridges. BRICK AND STONE VIADUCT. The brick viaduct at Maidenhead, constructed by Mr. Brune over the Thames on the Great Western Railway, is one of the finest specimens of that material. It consists of two elliptical arches, each 128 feet span, with a rise of 241 feet; the pier between the two arches is 30 feet in width; each arch, at the crown, is 51 feet in thickness, which increase gradually towards the abutments. Besides these two splendid arches, there are eight others, each of 28 feet span, four on each bank of the river. The stone viaduct over the Ouse, near York, on the Great North of England Railway, is another specimen combining great strength and elegance of construction. It consists of three arches, each 66 feet span, the width of the arches is 28 feet, their thickness at the keystone 3 feet, which gradually increases towards the springing, and the piers are 10 feet in thickness. The Vale Royal stone viaduct, over the river Weaver, on the Grand Junction Railway, has five arches, each 68 feet span, and 60 in height; the whole length of the viaduct is 456 feet. In the same railway, over the Mersey and Travell Canal, there is a viaduct of 12 stone arches, the central two are each 75 feet span, and the rest from 40 to 14 feet. The Quaker's Yard viaduct, over the Taff, in the Taff Vale Railway, has six arches; its height above the river is 100 feet, and its length 600 feet. There is another viaduct ir. the same line, at the junction of the Rhondda and Taff, having an arch 100 feet in span, and 60 in height. The Ouse Valley viaduct, in the London and Brighton Railway, is 1440 feet in length; it has 37 brick arches of 30 feet span, its height varying from 40 to 96 feet. The London and Greenwich Railway, and the London and South Western Extension are continuous viaducts; the former consists of more than 1000 brick arches, each 18 feet span, and 24 in height; the arches in the latter are a little wider, having, besides, several elegant oblique iron arches, for the purpose of crossing Westminster Road and other principal streets. The former is about four miles in length., and the latter nearly two miles. OBLIQUE OR SKEW BRIDGES. The Brampton viaduct, over the Gelt, on the Newcastle and Carlisle Railway, crosses the Gelt and a public road, at the height of 80 feet above the bed of the river. It consists of three stone arches of 33 feet in direct span, which are built at an inclination of 45°, thus making their oblique span nearly 50 feet each. The Fairfield Street bridge, on the Manchester and Bir This mingham Railway, has an oblique span of 129 feet, with a rise of 12 feet, and a direct width of 31 feet. It is composed of six ribs of iron, projecting before each other 13 feet, on independent abutments. Open wrought stone parapets crown this viaduct, presenting an agreeable and novel appearance. bridge was designed by Mr. G. W. Buck, being remarkable for its acute angle, which is only 244°. The weight of the iron in the six ribs or girders is 540 tons: the remainder of the viaduct consists of brick arches 45 feet in span. NOTE. Other lines of railway present a great variety of these bridges, both of brick and iron; some of which display great elegance of construction. This kind of bridge, it is said, was first introduced by Mr. Chapman, as canal aqueducts in Ireland. HIGH LEVEL BRIDGE, NEWCASTLE-UPON-TYNE. This bridge is of cast iron, and forms the viaduct of the Great North of England Railway across the deep valley of the Tyne. In addition to the elegance and magnitude of this work, it has a common carriage way suspended beneath the railway, thus giving it a decided claim to novelty of construction. The number of its iron arches are six. Each arch consists of four cast iron ribs, having a span of 125 feet, rising 17 n the centre. The ribs are disposed in pairs: one pair on each side of the carriage road. The carriage road is 20 feet wide. The foot roads (one between each pair of ribs) 6 feet wide. Total width of railway 33 feet. Weight of iron in each arch 576 tons; in the whole structure about 5000 tons. Height from high water to level of rails 108 feet; to suspended carriage road 85 feet; total height from bottom of river 128 feet. Length of bridge from the Castle Garth to Gateshead, inclusive of cast iron approaches, 1337 feet. WOODEN BRIDGES. The Ouseburn viaduct, on the Newcastle and North Shields Railway, has nine arches, of which two at the ends are stone, the other seven are of wood, on stone piers; the three central arches are each 116 feet span, and the two others each 100 feet. The whole length of the viaduct is 756 feet, and its height above the stream in the centre is 180 feet. The Willington Dean viaduct, on the last mentioned line, consists of seven wooden arches, of which five have a span of 120 feet cach, and the two exterior ones 115 feet each. The whole length of the viaduct is 1050 feet, and its height 82 feet. Wooden viaducts, on a smaller scale, abound in various lines of railway in this kingdom.-Wooden bridges on the lattice principle (first suggested by Mr. G. Smart, about 25 years ago, as applicable both to iron and wooden bridges), abound in the United States of America. One of them, over the Susquehannah at Columbia, has 29 spans, each 200 feet wide, the whole viaduct being about 1 mile in length. These viaducts can not be anticipated to be of long duration. The lattice principle has been considerably improved, and employed in wrought iron bridges by Mr. R. B. Osborne. This principle has been still further extended by Mr. W. C. Harrison, by adding tubular frames to the lattice work above and below, the upper one being bent like an arch. In a design made by him for a viaduct of this kind to carry a railway over the river Ouse, the span is 170 feet, and the rise of the arched tube above the horizontal one is 15 feet. The arched tube to be of wrought iron plates an inch in thickness, and its section to be 4 feet in depth and 3 in width, the horizontal tube to be a little less. For a double line of railway three of these bow frames are required. |
