Engineering Wonders of the World
Volume III

320 ENGINEERING WONDERS OF THE WORLD. girder to be fixed. When the wall had been securely pinned up above the girder, the sus- pended needles were put in one at a time, the intervening masonry being held up by cross steel joists placed on top of the needles. In. every case the deflection of the girders had been taken up by a system of folding steel wedges, which were driven up as the old foundations were cut away and the super- incumbent weight taken by the girders. The success of the whole operation was ascribed by the engineers in a great measure to the fact that grouting under air pressure had been extensively employed, especially in filling up interstices between the girders and the old masonry. The girders are supported on steel-work stanchions, resting on large bed plates formed of steel joists and plates laid on a concrete bed having a minimum thickness of three feet. Girders, stanchions, and bed plates were filled in solid with breeze concrete and grout ; and to guard against any possible deterioration through neglect of future painting, all were further encased in the same material. In this ingenious way the central structure of the church, weighing 500 tons, the south wall of 350 tons, and the north wall of 500 tons were successively brought to rest on seven main girders, each weighing from 25 to 30 tons—masses not easily handled in the very limited space available. The station booking-hall is 55 feet by 40 feet, and when all the lifts are in operation 350 passengers can at the same moment ap- proach or leave the railway. The whole work was carried out to the satisfaction of every one concerned, and when all was over the authorities of St. Mary Woolnoth offered to sell the church to the company! [Note.—Thanks are due to Mr. Francis Fox, M.Inst.C.Eand to Mr. David Hay, M.Inst.C.E., for assistance given in connection with the letterpress and illustrations of this article.}