MECHANICS AND USEFUL ARTS. 21 



pension chains or rods are held by a large mass of masonry built upon 

 a suspended plate, to which they are fastened. There are, however, 

 in order to give addifional security, back stay-rods at each end, which 

 run a considerable distance into the ground, and are fastened to mas- 

 sive oak frames, thus giving an additional resisting force of many hun- 

 dreds of tons of earth. 



PROPOSED SUSPENSION BRIDGE OVER THE DNIEPER. 



THERE has lately been exhibiting in London a large model of a sus- 

 pension bridge, which is about to be erected over the River Dnieper, by 

 order of the Emperor of Russia. When completed, the bridge will be 

 half an English mile long, thus forming the longest suspension bridge 

 in the world. It is proposed to have five piers, besides the two abut- 

 ments, making four openings of 444 feet each, and two of 222 feet. 

 The roadway will be 34 feet wide, with a footpath of 6 feet, and on 

 the Russian side of the river there will be a small revolving or swivel 

 bridge, by which the communication with the Polish side of the river 

 can be at once cut off. This swivel bridge will communicate with the 

 rest of the structure by an island formed of masonry, which will be 

 so constructed that any injury which happens to the chains within it 

 can be easily repaired. The work will, on account of its frontier sit- 

 uation, be strongly fortified, each of the immense piers on which the 

 chains are swung being intended to be mounted with cannon. Five 

 years will be required to complete this extensive structure. 



GIRDER BRIDGE ON THE MANCHESTER, SHEFFIELD, AND LIN- 

 COLNSHIRE RAILROAD. 



ON the Manchester, Sheffield, and Lincolnshire Railroad, a bridge 

 has just been completed across the River Trent, which is of a similar 

 character with the Britannia Tubular Bridge, but it differs from it in this 

 important respect ; that, instead of being intended for the trains to run 

 through the inside of the tube, the girders form the parapets of the 

 bridge, and the road-way is supported by transverse wrought-iron hol- 

 low beams, also of tubular construction. This bridge is called the 

 Hollow Girder Bridge, to distinguish it from the Britannia Bridge, and 

 it is the largest one of the sort yet constructed. The stone-work con- 

 sists of a centre pier and two elliptical arches of 50 feet span, termi- 

 nating by substantial abutments. The iron part of the structure con- 

 sists of two spans of 154 feet each, which with the land arches and 

 abutments give a total length of about 460 feet. The principal girders 

 are each 336 feet long, 12 high, and 3 feet 1 inch wide. The tops of 

 the girders are formed of two cells 18 inches wide and 12 deep, to re- 

 sist compression. The girders are fixed securely on the middle pier, 

 but on the abutments their ends are supported upon rollers, resting on 

 cast-iron plates, bedded into the masonry to admit of expansion and 

 contraction. On the outside of the girders are riveted two parallel 

 lines of angle-iron in the form of an arch, which spring from the mid- 

 dle pier to the abutments on each side. The two principal girders 



