MARVELS OF MAN'S MAKING.
VIII—THE FORTH BRIDGE.
HE mouth of the Forth has very nearly bitten Scotland in two, and anybody who wishes to travel from Edinburgh to Dunfermline would have to go a long way round if they objected to crossing the river. Formerly a great many people did object to this, because they knew that, although the voyage was only about a short mile, the great billows from the North Sea would meet them before it was over, and give them a very unpleasant time. So everybody who had anything to do with the Forth was willing that it should be spanned by a reliable bridge, and plans for carrying this into effect were frequently proposed. Indeed, arrangements were almost completed in 1879 for building a huge suspension bridge from shore to shore. The drawings were made, the estimates prepared, and the spades and trowels even beginning to work on the foundations, when, one sad December night, a terrible gale arose. All through the hours of darkness it roared and shrieked across the British Isles, working havoc upon sea and land, but, when morning came at last, few were prepared for the appalling catastrophe it had caused. Sweeping up the Firth of Tay, it had torn away a portion of the great railway bridge that crossed the inlet, and hurled it into the water. A train was passing over at the time, and plunged into the abyss with all its passengers. The terrible event shook public confidence, and we might almost say that the gale of that December night caught all the drawings and papers connected with the proposed suspension bridge over the Forth, and swept them from public favour.
Immediately afterwards, Sir John Fowler and Mr. Benjamin Baker (both celebrated engineers) came forward with an alternative plan of which no one could doubt the strength. It may perhaps be described as an arch-suspension bridge, because the design includes the strength of both styles; but engineers themselves call it a cantilever bridge.
| Building the Bridge. | The Forth Bridge at the Present Day. | Train crossing the Bridge. |
Work was begun in earnest in June, 1883, and the first passenger train crossed from shore to shore in March, 1890. At the place chosen for its erection, the river is one mile and one hundred and fifty yards wide. Nearly in the middle of the stream there is a rocky island called Inchgarvie, and on this the great striding giant would have to plant one of its ponderous feet. But Inchgarvie was private property, and trespassers were likely to be prosecuted. So the stepping-stone for the giant to place its foot upon could not be laid there until the island had been bought and paid for. This being done, a huge caisson, similar to those which we have seen sunk under the piers of Brooklyn Bridge, was floated out to the island, and there lowered on to the rock under water, and firmly bedded. It was followed by three others, forming, as it were, the four corners of an oblong, which is two hundred and seventy feet long and one hundred and twenty wide. Eight more caissons were built, four for each side of the river, and these were sunk on to beds of firm clay, some of them being as much as seventy feet below the surface of the water. On each caisson a stone pier was built to take the iron columns of the main structure, and thus we see the bridge was to cross the mile-wide river in three strides. Starting from the southern shore at Queensferry, the first group of four stepping-stones lie six hundred and eighty feet away. Then comes a leap of one thousand seven hundred feet to the four on the island of Inchgarvie, followed by a similar bound to the four near the northern bank, and then a half-stride again of six hundred and eighty feet to land.