further sum of 2800l. was paid. The island is now, therefore, the property of the Forth Bridge Railway Company.
It having been considered advisable to cover the whole area between the piers with staging, a commencement was made without delay. Owing to the nature of the bottom, which was all solid rock, it was found more expedient and safer in view of the exposed position, to make this staging of iron, and not of timber. The area of this staging ultimately amounted to more than 10,000 square yards, and the weight of iron used in its construction was between 1100 and 1200 tons. In view of this large expenditure for temporary purposes, it was deemed right to proceed on some system in the laying out the main line of girders. As the horizontal tubes, the horizontal girders between skewbacks, and the double cross of diagonal horizontal wind-bracing, required to be carried by the staging before they could be connected with the skewbacks and rivetted up, the main lines of the iron girders of the staging followed the centre lines of these members, the remaining spaces being filled in sufficiently strong to carry any weight which was likely to be put upon them during the erection of the superstructure. As this staging stood well the very severe tests to which it was subjected from various causes, and only yielded to a slight extent in places where it had been absurdly overloaded, it may not be amiss to give a few particulars as to its construction, shown in Fig. 20.
The upright columns or supports consisted of four angle-bars 4 in. by 4 in. by 1⁄2 in., braced together on all four sides by double crossbars of flat section, 3 in. by 1⁄2 in., the column being 2 ft. square. A cast-iron shoe, to which the four corner angles were bolted, formed the foot of the column, and it had a large boss in the centre with a 4 in. round hole through which a pin was passed going into the rock to a depth of about 3 ft.
The longitudinal main girders were 5 ft. in depth, and consisted of four angles 6 in. by 4 in. by 1⁄2 in., two in the bottom boom and two in the top boom, with gussets inserted between every 5 ft. apart for attaching the diagonal bracings, which were angles 6 in. by 3 in. by 1⁄2 in. placed alternately on one side or the other. The girders were carried by, and bolted to, cross-angles attached to the supporting columns. The girders carried safely a distributed load of about 6 cwt. to 7 cwt. per square foot up to 30 ft. clear span between supports. The columns were arranged in clusters of four, forming a square, the sides of which were 14 ft. taken at the centres of columns, and such clusters were placed immediately under the points of intersection in the girders of the structure overhead, or in fact in any place where much weight had to be carried. The four columns so placed were braced to each other by crosses of flat bars of heavy section 31⁄2 in. wide by 1 in. thick, the centre of the cross being formed by a heavy ring, the flat bars terminating at that point in 11⁄2 in. round with a thread cut upon them which passed into the ring. By a nut on either side of the ring the flat bar—the other end of which was bolted across the column—could be tightened or slackened as desired. Two or three sets of these bracings, according to the length of column, were bolted to each of the four sides of the cluster, the lower ones reaching in most cases to within a foot-or two of the bottom of the column having to be put on by divers. Generally speaking these clusters were placed about every 45 ft., centre to centre, and for intermediate supports, where necessary, single columns under each girder were considered sufficient, and these would receive transversely a pair of angle-iron cross-bracings between high-water and low-water mark.
The longitudinal girders run through the uprights, spaced 14 ft. apart, and they were braced laterally about every 25 ft. by a pair of cross-angle bracings carried from top boom on one side to bottom boom on the other side and vice versâ.
All the girders were made in regular lengths of bars, breaking joint at 5 ft.; they were marked by template and punched, and all parts except those for closing lengths were interchangeable. All holes were punched for 7⁄8-in. bolts. The girders weighed just 1⁄4 cwt. per foot lineal, including all bracing, the columns about 64 lb. per foot lineal, including bolts.
The whole staging was erected by overhang with derrick cranes in the following way: Starting from a cluster, the next columns forward would be lowered till they nearly touched the ground, the diver would then descend and examine the bottom, selecting a nearly level bit, or otherwise dressing the rock roughly. A few bags of concrete were then lowered to him, with which he made the bed into which the column was lowered. It was then strutted by one or two light battens to the already fixed work, a 4-in. jumper lowered in the centre of the column, and a hole jumped by means of a spring pole some 25 ft. long. The jumper was lowered through a tube 41⁄2 in. in diameter, which fitted into a socket left in the cast-iron shoe at the bottom, and acted as guide. The hole was jumped about 3 ft. to 3 ft. 6 in. deep; the jumper was then withdrawn, and a wrought-iron pin, 4 in. in diameter and 5 ft. long was dropped down the tube. The latter was then lifted up, and the diver descended to ascertain whether the pin had well entered into the rock. When the columns were fast, a length of girder was laid upon them on each side, and the crane advanced another section.
Across the longitudinal girders, 12-in. rolled joists weighing 56 lb. to the lineal foot were laid, being 21 ft. to 25 ft. in length, and therefore overhanging the girders from 3 ft. to 5 ft. The joists were bolted to the girders by hook bolts and ordinary draw-washers, and were spaced 5 ft. apart. The decking consisted of 3 in. by 9 in. planking, bolted to the top flanges of the rolled joists by bolts and draw-washers from underneath.
The staging, as first projected, was commenced in the autumn of 1883 and finished before the end of 1884, but additions became necessary from time to time to accommodate the immense quantities of material, and at times the 10,000 square yards of staging were found quite inadequate to meet the demands upon it.
All portions of the staging which had to be used as landing places for materials—and of such there were a good many—had the iron columns strengthened by bolting on heavy timbers, with half-timber fendering upon that for wear and tear. Horizontal timber struts were also set up against the backs of those columns, to guard them against bending in by the action of the boats and barges upon them in rough weather.
By the time the staging was up round the north piers on Inchgarvie—these were already well forward—arrangements had to be made for the reception of the two heavy caissons for the south piers. Facing the south, therefore, two semi-circular openings were left about 73 ft. in diameter, an extra number of columns were placed in the half-circle and well braced with the others next behind, and the whole row of columns between the north and south piers, on either side, were joined together at about low-water mark by a continuous line of double angles to take the thrust from and give resistance to any possible bumping of the heavy caissons during the time they required to remain afloat.
Meanwhile plant and machinery were sent here as to the other centres, a number of offices, large workshops, stores and shelters for the men were built; also engine-houses for pumping engines, air compressors, hydraulic accumulators, electric light machinery, and much more.
Transport and Distribution of Material.
The supply, the transport, and the distribution of the materials necessary for the building of foundations and piers containing some 140,000 yards of masonry and also of some 55,000 tons of steel, and a more than equal amount of temporary appliances, was no mean task, and required the exercise of much energy and skill as well as tact and patience, for the work was equally pressing on all points, and no one liked to be left behind in that great race for supremacy.
Of the building materials, granite, Arbroath rubble, and sand were brought by water, and could, therefore, be unloaded at the various centres where required; so also could rafts of timber in baulks and planks or battens in barges, and in some instances cargoes of coal or coke, but all the other material had to come down the incline, and for these the jetty at Queensferry was the main centre of collecting and storing, as well as of distributing to the other jetties.
The steel for erection, after it had passed through the shops and had received a coating of boiled oil, and its distinguishing markings both in typing and stencilling, was passed down the incline on trollies and charged into steam barges for general distribution.
For the service of carrying materials were provided, four steam launches for the light work, and eight large steam barges, with a number of ordinary barges or lighters, which were towed by one of the launches or barges.
For the general service of conveying the workmen from or to, or between, the different main centres, a paddle steamer was hired for some time, which was afterwards replaced by one specially built for these works, and capable of carrying 450 men at a time. The steam barges, which were decked over, and the steam launches, were also used for the same purpose, as well as for the service of the engineers and other officials belonging to the staff. A large number of ordinary rowing boats were also kept in use, one of them, manned by two expert watermen, being attached to each cantilever for the purpose of saving life, should any man be unfortunate enough to fall from the erection. As a matter of fact these boats saved at least eight lives, and they saved fully 8000 caps and other garments which the wind had blown off the bridge.
Soon after the works had got into full swing it was seen that the accommodation at South Queensferry and North Queensferry and the adjoining villages, was totally inadequate for the number of workmen employed, and arrangements were made with the North British Railway Company to run trains between the works on the south side and Edinburgh, and between the north side and Inverkeithing and Dunfermline. These were all special workmen's trains and were run at merely nominal fares, the price for an Edinburgh weekly ticket being 2s., or 2d. for a run of over 13 miles. The Dunfermline tickets were about half that amount.
Two trains were run in the morning, closely following one another, and two trains at night, each train bringing a number of men going on their shift, and taking back those who had worked their shift. Some time later the train service was extended as far as Leith. It is worthy of remark that the men living at Leith, and there were several hundreds, had to leave their homes at 4 a.m., in order to be at their work at 6, and they would not on their return in the evening, reach home again before 7 o'clock, yet they preferred this to the other alternative of living in the overcrowded rookeries of the neighbourhood.
In the summer time a steamboat service was also arranged between the South Queensferry Jetty and Leith, viâ the Firth of Forth, calling both ways on Inchgarvie, and so long as the weather was favourable, this was a most enjoyable, and certainly healthy trip for the tired workmen.
On wet and stormy days, when the men had to leave work owing to the weather, these trains were often telegraphed for, to enable them to return to their homes, instead of keeping them till nightfall and leaving them to the tender mercies of the public-houses, of which there were in this place, as in many others, far too many.
As it was not possible to so arrange that the workmen living on the south side or north side of the Firth respectively, should be working on the same side, and as the Inchgarvie men also belonged to both sides, it required quite a fleet of steamboats and barges to convey the men to the points whence their trains started, the more so as this had to be done within a very short time after work had ceased. In bad weather, or during fogs, and on dark mornings and nights the transport of many hundreds of men—some nine hundred working on Inchgarvie alone at one time—was a subject of unceasing care and anxiety to those in charge, for in addition to the dangers provided by the elements, there was always a number of unruly and reckless men whose conduct brought mishap and injury on others as often as on themselves.
Lighting.
The efficient lighting of so large a working area, changing every day almost, having not only to be carried forward with the work, but also upward and in all directions, was a task of considerable magnitude, and of the greatest influence upon the rate of progress. It is not so much the lighting of the actual spot where work is proceeding, but that of the approaches to these points, and of the accessory places, such as stores, engine-houses, workshops, jetties, and landing-places, which runs away with so large a proportion of the total illuminating power.
As regards the nature of the lights it was to be expected that a keen rivalry would spring up between the various systems of lighting. South Queensferry has only a small supply of gas, and that at the ruinous rate of 8s. 4d. per 1000 cubic feet; this mode of lighting was therefore out of the race. Electricity was at once resolved upon—arc lamps for the shops, and outdoor work, and incan-
