Engineering Wonders of the World
Volume I

210 ENGINEERING WONDERS OF THE WORLD. feet per working minute. In 1857 were sufficiently advanced for the Preparations for Build- ing the Tubes. 13 cubic the piers second part of the construction to be com- menced—namely, the building of the huge iron tubes. The reader may remember that in the case of the Britannia Bridge the largest central tubes were built on the shore, transferred to the bases of the piers on which they were to rest, and lifted to their final position by hy- draulic presses. For the Vic- toria Bridge this plan was not feasible, and it was necessary to build every tube in situ on strong trusses of timber sup- ported on piles. On the upper chords of the trusses were laid rails for the travelling cranes used in the erection of the iron work, which were brought up to the scene of operations upon trucks. The platforms that decked over the space between the lower chords of the trusses were about three feet below the under- side of the tubes. ’ On the platforms were laid three longitudinal lines of timber, carefully levelled to form a foundation for the iron- work. It is not necessary to describe the process of assembling the tubes, but we may dwell for a moment upon the extreme accuracy with, which the plates had been pre- An Example pared in the works at Birken- head. There every piece of of Careful Manufacture. ^ron before being shipped was given a number corresponding with one on the plans. Each tube contained nearly 5,000 pieces, but so orderly was the arrangement that when they arrived at the bridge site the workmen had no difficulty in sorting them out and building every part into its allotted place. A further proof of care is well exemplified in the components of the central tube, which numbered more than 10,000 and contained nearly 500,000 holes. Not a single piece required alteration, nor had a single hole been punched in the wrong place. The End in Sight. It was well that the manufacturers had carried out their part of the work so faithfully, for the incorrect spacing of but a few rivet holes might have caused delays costing thousands of pounds. During 1857 eleven tubes were erected, and it became evident that with good luck the next season would see the completion of the central piers, and also of two temporary piers between them to sustain a Howe truss ex- tending across the opening to carry the central span during erection. It was of the utmost importance that all preparations should be finished before the winter of 1858 closed in ; nothing more could be done when once the ice-shove should have commenced. The men, now on their mettle, worked nobly, and the temporary piers were placed before ice began to appear. Great anxiety was ex- perienced as to whether these cribs would be able to withstand the shove. Under the test they proved equal to the strain, and as soon as the ice-bridge had formed, gangs of men transported huge quantities of materials to the stagings. The ironwork of the great central span had to be completed before the ice broke up in the spring; for, if the supports were moved at all with the span still incomplete, a disaster was inevitable. In spite of the intensely cold mists which, rose from the water below and caused frost-bite, though the men all wore the heaviest clothing, work proceeded by night as well as by day. The tube grew quickly, and its increasing weight caused its temporary supports to give gradually under the strain. When the amount of deflection at last became serious, a large number of screw-jacks were inserted under the tube to lift it to the proper camber. About the middle of March 1859 a terrific storm de- stroyed some of the scaffolding erected at the side of the tube, and this was followed by heavy rains which rendered the ice very rotten Working against Time.