The account of the Forth Bridge given at the working
men's meeting of the British Association last Saturday evening is very striking. In effect, the engineers have stretched six horizontal Eiffel towers, at a height of 370 ft. above high- water mark, across the estuary, and have yet made their structure capable of supporting, not only its own weight, but that of five of our largest ironclads, were they to be hung from. its girders. The problem presented to the builders of the bridge was the spanning of a space a mile-and-a-half broad. The water was too deep to allow the sinking of piers, and so the only plan possible was to utilise a rocky island in the middle of the Forth. Two great cantilevers, or brackets, 700 ft. long, were pushed out from each side of the space to be spanned, and then connected by a steel girder 350 ft. long. The weight of the metal employed is 50,000 tons, and yet the structure may be depended upon to carry an additional weight of over 14,000 tons, while three-times the fury of the worst storm ever recorded can break upon the bridge without the slightest danger. The work is undoubtedly one of the greatest, if not the greatest feat of engineering ever per- formed. Oddly enough, the cantilever principle of construc- tion, though it has long been in use in China, was never employed in Europe or America till the publication of the designs for the Forth Bridge. It is likely, however, to become common enough in the future.
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