The Works Of Messrs. Schneider And Co.

THE ALEXANDER III. BRIDGE; FLOATING BRIDGES. 145 the whole of the inovable centres ; these centres are made , pleted. It also shows the means aclopted for its érection. to advance in one operation by means of screw-jacks. In practice it has been found that ten days are sufficient for the foreman to effect all the operations required for the putting in place a pair of ribs ; these operations involve the bringing of the segments on the spot, their fixing, adjustment, freeing the rib, and shifting the roller bridge and centres to the following group of ribs. The setting free of a pair of ribs is made at intervals of one month. in order, when the roller bridge is over one group of ribs, to erect, by means of the steam winches, all the corresponding heavy parts of the superstructure, such as uprights and stays, string - pieces, girders, &c. It is not necessary, therefore, for the roller bridge to be brought back for these operations, as the less heavy These means, owing to their importance, have involved considérable outlay ; but Messrs. Schneider and Co. were desirous of completing the érection within the time pre- scribed, so that the bridge sliould form part of the great Exhibition of 1900. Floating Bridges (Figs. 465 to 476, Plate XCIIL). -—Messrs. Schneider and Co. have made a very minute and complets study of the problem which consists in re-establishing the working of a railway from one bank of a river to the other, when it has been tempo- rarily stoppée! owing to the destruction of a viaduct. Let us suppose a river 450 metres (1,476 ft.) wide, the currents of which have a rapidity of 3 metres (9 ft. 10 in.) per second, the height of the water varying by 3 metres Fig. 464. pieces can easily be shifted from a movable flooring resting on the ribs. The érection of all rolled material, while offering certain difficulties in exact fitting', is effeeted rapidly, owing to the small number of rivets that have to be put in place on the spot. The amount of the work, as regards tonnage, being approximately as follows :— Tons. Weight of cast-steel arcs ... ... ... ... 2,000 ,, corresponding rolled material ... 2,000 ,, viaducts on shore ends ... ... 450 ,, tramway coverings ... ... ... 250 ,, abu tmen ts of same ... ... ... 100 cast steel for tynipanum shoes and kerbstones ... ... ... ... 250 ,, cast iron ... ... ... ... 250 5,300 The above description will give a general idea of the Alexander III. Bridge as it will appear when com- (9 ft. 10 in.). The traffic per day of 12 hours that is to be carried between the two banks, amounts from 280 to 480 effective tons, depeneling upon the use of one or two floating bridges. The loads have to include locomotives, wagons, or troops, the weight of the locomotives being calculated at 54 tons and 64 tons. After carefully looking into the matter, and taking into account several examples of profiles and nature of ground ; the. varions ways in which the loads would be divided ; thë varions methods of taking apart and trans- porting the apparatus, &c., Messrs. Schneider and Co. aclopted the following material : 1. A floating bridge (Figs. 465 to 469, Plate XC1I1.) of a total weight of 61 tons, formed of 15 sections of 2.400 metres (7 ft. ]0| in.), bolted together, with the interposition of india-rubber packing, in order to insure their being perfeetly watertight. The ends of the floating bridge being bevelled enablé