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.

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.

The three sets of caissons once being in their places, and the stone piers built on top of them, people at last began to see the beginning of the Forth Bridge. From each of the four piers in each group there slowly rose a huge steel tubular column, twelve feet in diameter, each pair leaning inwards, so that though at their bottoms they stood one hundred and twenty feet away from the pair on the opposite side (that being the width of the base of the bridge), the head of both pairs were only separated by a distance of thirty-three feet. This was done to afford greater resistance to the wind. Each group of four columns forms what are called the towers, and rises to a height of three hundred and thirty feet. They are firmly braced together by tie-girders and cross tubes nearly as large as themselves. They were erected section by section, rivets and hammers being used instead of trowel and mortar. Scarcely were their summits united when, from their feet, there began to spring on either side the great tubes forming the lower part of the arch. In the cantilever construction, the bridge grows right and left from its piers at the same moment, because balance must be maintained. As the lower arched tubes just mentioned stretched further over the water, sloping girders started downward from the tower top to meet them, and they were soon connected by lighter cross-ties. Tubes were used for the arch because they are best suited to bear the compression strain caused by a train passing over the bridge. The girder form was chosen to stretch downward from the tower top because it is better able to bear the tension or pulling strain. They together form what is called a cantilever; if you lay the letter V on its side, the open end will represent roughly the place where the arch and girders start from the tower. Thus we see how the two strengths of suspension—cable and arch are combined in the Forth Bridge.

When the sets of cantilevers from the grouped piers had grown out toward one another till they were separated by only three hundred and fifty feet, the gap was spanned by a connecting girder, the joints between it and the cantilever being sufficiently loose to allow of the expansion and contraction of the great bridge with the changes of temperature.

The two 'skeleton towers' on the north and south sides of the river are not so wide as the one on Inchgarvie, because their shoreward cantilevers are supported on strong stone buttresses, whereas the Inchgarvie cantilevers are both stretched out to the connecting girders only. The broader base helps to prevent the bridge see-sawing when a heavy train goes over it, and it is further assisted by the landward ends of the other two cantilevers being heavily loaded. This prevents them 'tipping up' when the train has crossed the first tower on its way across the river.

It is easy to understand that such a mighty work was not accomplished without great danger, and it is surely a wonder that the knowledge of this danger did not make the workmen careful. Yet frequent accidents occurred entirely through their indifference to peril.

On one occasion a company of riveters were working on a platform which was being slowly raised to the summit of one of those lofty towers. Suddenly the winch at the top, by which they were being hoisted, refused to act, and instead of looking down to ascertain the cause, the men continued to force the handle of the winch round till the toothed wheel broke. Down went the platform with its gang of workers, crashing from girder to girder, and striking other men headlong into the air, to be killed or wounded among the network of girders far below. This terrible accident caused the death of three people. A constant source of mishap was the thoughtless dropping of tools from great heights, and no appeals would induce the men to lay their implements down instead of throwing them from them as soon as done with. The authorities themselves did all they could to preserve the health of their men. Warm clothing was supplied to them, and even warm food and shelter were to be found on the summits of those windy towers, and out on the ends of the cantilevers over the icy river. Portable stoves in small kitchens were built in the most precarious positions, and a man could dine there as comfortably on a stormy day as in his own home.

Those who are fond of figures will be interested to learn that this enormous structure weighs fifty-one thousand tons, and is held together by nearly seven million rivets. It cost three million pounds, almost enough, one would think, to cast the stepping stones on which it rests in solid gold.