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and weeks lost through waiting for crossings or junctions to be built up and completed, and although much of this may be said to be due to the novel character of the work, yet it is a point which must not be lost sight of. Elsewhere, it has been stated that owing to the general batter of the sides of the structure, and owing to all of its members being out of the perpendicular, as well as the horizontal, they had a natural tendency to either fall together, or else apart, and in both cases apt to be both out of the right direction. Thus in building out a pair of struts or ties, so soon as a length of 30 to 40 ft. had been built, it became necessary to put up temporary girders to hold them apart or keep them together, and a large amount of dangerous work had to be done before a further section of work could be built. The members themselves, even when only bolted up, were often so stiff that hydraulic rams had to be used to force them apart or draw them together. In other cases wedges of hard wood and union screws were able to deal with them. In looking at the illustrations and plates showing various phases of the erection, this feature will immediately attract attention, and in many cases it must be difficult for any one except those conversant with the structure to distinguish between temporary and permanent work.

For reasons explained above, and easily understood, it was not possible to fix the wind-bracing so close up to the new work that temporary appliances could be dispensed with, and therefore an immense number of lattice-girders, some heavy, some light, had to be used to allow the permanent members to be corrected, and when corrected held in position. In the bottom members, especially near the piers, where they were some 120 ft. apart, centre to centre, the temporary girders naturally had to be very strong and heavy, but after the completion of three bays, timbers were in most cases sufficiently strong to take all resistance, and this much simplified matters, for timber is both light in weight and easy to cut and shape to requirements. Thus in the bottom members alone, at every vertical tie and at every junction, the necessary corrections required the placing of temporary struts and wire rope ties, and in most cases when finally fixing the horizontal wind-bracing girders, similar girders had to be placed to fix the position of the member. A repetition of this kind of work with every tie and strut, in bottom members and top members, at every vertical tie, and at every intersection, made up an amount of work of which no visible trace is left, yet which was as real in its day as any which helped to build up the mighty fabric.

The Use of Wire Ropes.

Of all appliances in use during the erection none have given more unmixed satisfaction than steel wire ropes. It may be considered a rash guess, though the writer at any rate has no hesitation in making it, that the list of accidents would have been doubled at least, and a great deal more time and money expended, but for the absolutely reliable character of this article, and for its manifold uses.

In the first instance there were nearly a score of cages or hoists for the raising of men and materials to the different levels at which work was carried on, and these were going continuously day and night for several years, and there is not a single case on record of a rope having given way without having given ample warning. At first the pulleys over which the ropes passed were rather small in diameter, and the result of continuous running was that single wires commenced to give way, but with a crackling noise which soon became known to the attendant at the hoist. With the introduction of pulleys of 3 ft. 6 in. in diameter, and guide pulleys not smaller than 18 in., and having the bottom of the grooved pulleys laid with hard wood, the ropes lasted three to four times as long, that is from nine to twelve months. Even when taken off the hoists, moreover, they were quite good enough to act as guide ropes to the cages, or to support steady weights when used as pennants, or as temporary ties between the various members of the structure.

OIL FURNACES FOR HEATING ANGLE BARS
OIL FURNACES FOR HEATING RIVETS

All cranes used upon the erection had their chains taken off by degrees, and were supplied with wire ropes instead, which did the work more quietly and with far more safety and reliability. Still more useful were the ropes when portions of overhanging girders or other members had to be temporarily suspended from other portions already fixed. In these cases, by means of union screws attached between the girders and the ropes, the former could be raised and lowered at will and held in position until a joint with other portions of the work was made. Thus in the central towers, once they were completed, everything within the area could be suspended, and thus the internal viaduct was built in the easiest manner possible, every length in succession being held up until the girder was complete and able to carry itself. And thus in the same manner while building out the bottom members in cantilevers, the vertical ties and struts, and later on the wind bracings, a few wire ropes attached to the upper members, as far back as necessary to obtain a fixed hold, held up—and if required drew up—the overhanging ends to any desired position.

It is only necessary to call attention to the weight of these ropes in comparison with that of chain cables and hemp ropes of equal strength, to see at once the great advantages which the use of these ropes offered for the particular kind of work which had to be done at the bridge.

Circumference of Wire Rope		Weight per Fathom
		Wire Rope		Cable chain		Hemp Rope.
4	in	12	lb	54	lb	33	lb
3	,,	7	,,	30	,,	19	,,
2¼	,,	3¾	,,	21	,,	11¼	,,