Page:Forth Bridge (1890).djvu/42

Rh All materials for building were raised to the girder level by means of two hoists stationed at either end, and the materials so raised were run on trollies by boys or drawn by Shetland ponies to the places where they were required. Thus granite blocks, Arbroath rubble, and mortar, were all prepared on the jetty below and lifted up.

To assist the masons in their work of laying granite and rubble an overhead traveller was placed to each side of every pier. All these travellers were worked by friction gear and clutches, both for hoisting and lowering, or for travelling, an endless wire rope being run along the girders from end to end, driven by the same engines which drove the pumps during lifting.

When the seven spans had thus been raised to 47 ft. above high water, the next two spans from pier 3 to pier 1—which in the meantime had been erected on staging passing over the Edinburgh-road—were joined on, and the further lifting proceeded with in the same manner as before. The last span from abutment to pier 1 had meanwhile been erected on staging at level 119 ft. above high water, and was joined on when the other girders reached that level, the complete viaduct being then raised through the remaining 11 ft.

The first lift at South Queensferry was made from level 23 ft. above high water in May, 1886.

Level 47 ft. above high water was reached August 10, 1886.

Level 91 ft. above high water was reached February 15, 1887.

Level 119 ft. above high water was reached June 14, 1887.

Level 130 ft. 6 in. or top was reached August 7, 1887.

No mishap of any kind occurred in the course of this work, and in no case did the granite facing or rubble backing show the least sign of giving way during the underbuilding of the piers under this considerable load.

After the girders had reached the tops of the piers the cross girders and hydraulic rams were removed and the bedplates substituted.

In all cases the thirteen viaduct piers had the hearting constructed of concrete up to the level at which the girders were built, but from the time lifting was done Arbroath rubble was used exclusively, as it was feared that the concrete could not set sufficiently hard in the time allowed between the lifts, while the Arbroath rubble masonry set firmly and solidly in about thirty hours.

Very little staging was used in this mode of erecting, most of the timber being used over and over again, for as soon as a girder was rivetted up and could carry itself across the span the staging was removed from under it, and was transferred a span further forward.

After the piers were in position the temporary connections at the joints where provision had been made for expansion and contraction were removed, and the remaining buckle-plates on the top and the wind-fence on both sides were put on.

After several coats of paint had been put on the