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in another part of this report, how the stability of the whole bridge dependsupon its proportions.
Each of the two spans measures 788 feet from centre to centre: the length offloor between the abutment and pier is 748 feet.
Two isolated towers of 30 feet high and at a distance of 30 feet apart fromcentre to centre, are erected upon each abutment, for the support of the cables.The latter rest in cast iron saddles, which are allowed to move on rollers, forthe purpose of adjusting the tension of the land cables, as they contract orexpand, either from changes of temperature or from loads. The castings whichsupport the cables upon the centre tower, are stationary and not allowed tomove.
The floor of the bridge, which is divided into carriage-way and two side-walks, is to be composed of timber and plank, and to be suspended by means oftwo wire cables and a number of wire stays. The arrangement and construc-tion of all these different parts will be more fully explained in the next para-graphs.
The end of each cable will be spread out in seven parts, which will connectwith as many chains, manufactured in solid bars of the best hammered charcoaliron, similar to those which I applied on the Monongahela bridge and on theaqueduct at Pittsburgh . The plan of anchoring which I propose for this workwill, in its main features, be but a modification of the plan applied at Pittsburgh .Each of the seven anchor chains will descend by itself through the masonry ofthe return walls, not in a straight, but curved line, the last link occupying avertical position, and connecting with a cast iron plate of great strength, whichsupports the foundation of the superincumbent masonry. The whole arrange-ment will be such, that no unequal settling, which would slacken the one chainand tighten the other, can take place. In proportion to the magnitude of theforces, adequate means will be applied to meet them. These forces can all beaccurately determined and estimated, and, therefore, be controlled with safety.As the success of the anchorage, however, depends much upon the resistance ofthe masonry, the necessity of a very careful construction of the return wallsbecomes evident.
5. CABLES.
The floor of the bridge is to be suspended to two wire cables, of 11.28 inchesdiameter each, by means of suspension rods. They will be prepared in theplaces in which they are to remain, and suspended in a somewhat inclinedposition between the roadway and the sidewalks. The formation of these cablesis to commence after the completion of the masonry and of the anchorage.A rrangements similar to those used on the Pittsburgh aqueduct, but on a moreextensive scale, will be made, and my patent machinery applied for the traverseof the wires across the river. Each cable will be composed of an assemblage of5500 wires of one-eighth inch thick. When laid, they will be wrapped by wireof a smaller size, by means of my patent wrapping machine. A cable thusfinished, presents the appearance of a perfectly round, smooth, and solid cylinder,