The Works Of Messrs. Schneider And Co.

MILITARY BRIDGES; THE CHANNEL BRIDGE. 149 forming device, but with single piles), reduces the span to 3.500 metres (11 ft. 6 in.). The superstructure is calculated for a concentrated load of 400 kilogrammes (say 8 cwt.), or a uniformly divided load of 250 kilogrammes (say 5 cwt.) per metre run. The superstructure can be made up in sections of sizes suitable for transport by mules ; this was done with the bridges suppliée! by Messrs. Schneider and Co. to the Argentine Republic. A bridge can also be built up simply by wood girders or logs found on the spot, as lias been done in Switzerland, Spain, Sweden, &c. The érection of the bridges is a very simple operation. The intermediate support and the bridge-forming device are first applied to the shore end of the superstructure ; two to fix their trestles ; it is also well adapted for Crossing narrow gorges. b. Bridges for ail Corps of Military.—Only a few modifications of the above method of bridge construction, are necessary to facilitate the Crossing of rivers by ail corps of troops. The bridge-forming device and the intermediate bearings are arranged for placing side by side, two widths of superstructure; the width is thus increased to 2.400 metres (7 ft. 10J in.), and is therefore sufficient for wheeled traffic and horses. Channel Bridge.—One word in passing concerning this scheine, in which so many engineers have been eagerly interested. When the company that had been formed for designing a bridge over the channel applied for Government Fig. 494. The Pfund System of Military Bridges. men stand forward, holding each a pile at an equal angle (about 60 deg.). Each man drives a pile at this incline in the bed of the river, and tightens the socket at command of the superintending officer ; each then takes hold of the second pile. The squad push forward the superstructure and this advances, describing an arc of circle, the centre of which is the bearing point of the pile in the bed of the river. On command of the officer the squad stops the forward movement of the super- structure ; the second pile has been brought in front of the first one, the two together on each side forming an X- The two men previously mentioned then drive this second pile, and the operation is proceeded with in the same way until the bridge is laid. The forward movement takes a maximum of one minute for a 2-metre length of superstructure. This method can be followed in places where pontooneers would not be able approval (1894), submitting the design worked out in every detail by Messrs Schneider and Co., and, as regards the foundations, by Mr. Hersent, the execution of this work seemed nearer realisation than at the present time. It is possible, however, that in the future a fresh. current of opinion will set up in favour of the execution of such an important work. Therefore, the bridge designed by Messrs. Schneider and Co. is still of aetual interest. The calculations prove, without a doubt, that it is possible to build a gigantic viaduct, notwithstanding what has been said to the contrary ; it will consequently be of interest to describe the main points of the design. The proposée! bridge (see Fig. 503) is 33,450 metres (20| miles) long; it is in a straight line, and the greatest depth is 51 metres (167 ft.). Along its whole length the sea bottom consists of heavy chalk beds. Messrs. Schneider and Co.’s design embodied spans of 500 and 2i