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the great depth of water in the two main channels—above 200 ft.—and the high ground upon both shores, would necessitate very steep gradients and long approaches—making the tunnel many miles long, irrespective of the uncertainty of the nature of the ground through which the tunnel would have to be cut.
All things considered, the most suitable site for a bridge was held to be that at Queensferry; and, owing to the great depth of water and the nature of the bottom of the estuary, it was not considered expedient to construct a bridge with shorter spans than those which are indicated by the natural configuration of the ground.
The original design for a continuous girder bridge (see Fig. 4)—on the cantilever and central girder principle which had been submitted by Messrs. Fowler and Baker—was in some particulars modified to suit the conflicting views of the other consulting engineers, and was then submitted to the directors in May, 1881. After consultation with the officers of the Board of Trade, this design (see Fig. 5) was finally adopted, and Messrs. Fowler and Baker were appointed engineers to carry it into execution.
_Fig._1,_Page_3.png)
Fig. 1. Anderson's design for bridge over the forth, 1818.
In July, 1882, an Act of Parliament was obtained authorising the construction of the bridge and sanctioning the new financial arrangement by which the capital of the Forth Bridge Company was guaranteed with interest at 4 per cent. per annum, each of the four contracting railway companies undertaking to find its share of the capital expenditure and pay its share of the interest. It is also agreed that the North British Railway Company will maintain the per-
