carried over the bridge. There is no difficulty in fulfilling or combining these conditions in a square bridge, but it is different with the oblique sort. Of the kind of bridge which is commonly employed to obviate these difficulties, and to secure the greatest advantages, the accompanying engraving of Winkwell Skew Bridge is an illus

The larger bridges on our railways usually traverse rivers or canals; the smaller ones cross common roads. These are sometimes handsome erections. One of the best finished of them is near Rugby (see p. 172), of yellow brick, with stone dressings, and is a clever adaptation of the castellated style. As viewed from one side, some of the arches of the large Midland Viaduct appear in the distance. Bridges of this kind, however, are not common, it having been ascertained that such works may be erected more economically by means of iron girders, as is the case with several railway bridges which cross streets in the metropolis.

One of the most remarkable structures in the country, of the kind, is the bridge which carries the Great Western line over the Thames at Maidenhead. It is composed of a central pier and two main arches, flanked at either end by four smaller openings, intended for the passage of the water during floods. The main arches are

elliptical, 130 feet span, and 24 feet rise. The land arches are semicircles of 28 feet diameter. The central pier stands in the middle of the river. The foundations of the bridge rest on a hard pebble conglomerate, overlying the chalk, and covered up by loose gravel and alluvial mud. The body of the work is executed in brick; the cornice, cap-stones, and coping are from the quarries of Bramley-Whitehurst, near Leeds. The bridge has this peculiarity

it consists of two arches only, and these are probably the largest, and certainly the flattest, in proportion to their span, yet executed in brick. Its structure was minutely commented on at the time, and many absurd misrepresentations were made in reference to it.

The reason of its construction with two arches instead of a greater number was the existence of a shoal, affording an excellent foundation in the middle of the river, and the necessity of leaving the sides and deeper part of the stream open for navigation. On the other hand, the importance of preserving the gradients of the railway uniform, governed the height of the arches.

There is a kind of bridge on the South Coast Railway which is worthy of notice. It is over the Arun, below Arundel, and is the first of its kind. At this point the Company was bound to leave a clear water-way of sixty feet for the passage of shipping, and this had to be accomplished by a contrivance called a telescope bridge. The rails, for a length of 144 feet, are laid upon a massive timber, platform, strengthened with iron, and trussed by means of rods, extending from its extremities to the top of a strong frame-work of timber, rising thirty-four feet above the level of the road-way in the middle of the platform, the framework being ornamented so as to appear like an arch. Beneath this central framework and one-half of the platform are mounted eighteen wheels, upon which the whole structure may. be moved backwards and forwards, so as either to be quite clear of the river, or to project its unsupported half across it, to form a bridge for the passage of the trains. To provide for moving this platform, when it is necessary to open the water-way, a second portion of the railway, sixty-three feet long, is laid upon a moveable platform, which may be pushed aside laterally, while the

end of the larger platform is pushed longitudinally into its place. Two men and a boy are able to open this bridge in about five

minutes, the operation being performed by means of toothed wheels and racks, wrought by winches.

A steam-bridge, or floating railway, recently constructed to cross the Forth, between Granton and Burntisland, on the Edinburgh, Perth, and Dundee line, deserves special notice. The difficulties that had to be overcome to obtain uninterrupted communication between the two portions of railway were considerable. As the tide rises about twenty feet, a vessel on a level with the quay at high water would be a long way below it at low water; and some special means had, therefore, to be adopted of putting carriages and wagons on board, that they might be transported to the other side. Hydraulic or steam cranes were, it is said, first proposed, by which they might be raised or lowered; but it was found that this would be too slow and expensive a process, and that danger would also be incurred of injuring the vehicles. A floating bridge was next suggested; that is, a set of girders and beams, having one end hinged on shore, and the other attached to a float, to rise and fall with the tide. This, it is considered, would have fully answered the purpose, were the water always smooth; but in stormy weather it would have required protection by means of expensive piers and jetties.

The plan that has been adopted was designed and executed by Mr. Bouch, the manager of the line. Alongside the piers at Granton and Burntisland an incline of masonry has been built, upon which are laid two lines of rails of the usual gauge. Upon this incline a heavy moveable platform is placed, sixty-one feet in length by twenty-one in breadth, and resting upon sixteen wheels. To the front of the platform are attached, by means of universal joints, four malleable iron girders, thirty-five feet long, constructed of boilerplate, spanning the requisite distance from the platform to the vessel, and affording sufficient depth of water for the keel of the steamer to clear the surface of the slip. These girders are elevated and depressed for the arrival and departure of the vessel, by means of a winch on each side of a staging, eighteen feet high, erected across the platform. The whole structure, with the girders, is raised or lowered to suit the different heights of the tide, by means of a small stationary engine, which is also employed in moving the trucks off and on board the vessel.

The arrangements are made in so complete and efficient a manner, that the vessel can be loaded or discharged with the greatest facility, -five minutes being sufficient to place on board thirty or forty wagons, or to remove them from thence to the shore.