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the curvature at the centre, and also the deflection, will be increased. Thecables will be relieved, and consequently rise as far as the floor is supported bystays. Making our calculations for a full catenary, this will amount to 300 feetat each end, or 600 feet altogether. The length of the floor, as far as supportedby the cables, is therefore reduced to 580 feet, for which the tension should becalculated. By introducing the proportions of the original full catenary intoour calculations, we shall get a result too high, and shall, therefore, be on thesafe side. The maximum weight of 580 feet of floor, cables, and maximumload, is 870 tons, and the tension resulting from this weight is found to be 1,427tons. My practice is to allow 7 wires of 1-8 inch thick for every ton of maximumtension. The cables would therefore have to be composed of 9,989 wires; inplace of this I have proposed to employ 11,000, as was stated in the 5th sectionof this report. At the rate of 7 wires per ton, each wire will bear 285 pounds,while it is capable of supporting a weight of 1350 pounds, or more than fourtimes as much as the greatest tension to which it can ever be subjected.

The constant weight of 1 foot of floor was stated at - - 1,100 pounds.

Weight of cables and saddles, - - - - - - 600 “

Total,.1,700

The tension resulting from this constant load is equivalent to 161 pounds perwire, or not quite 1-8 part of the weight which would cause a rupture. On thePittsburgh aqueduct, where the weight is nearly constant and uniform, I haveallowed five times the quantity of wire, which would barely support it.

The above allowance for the strength of the cables, might indeed be consid-ered extravagant. But we have to remember that this bridge will have toaccommodate an immense traffic, and that it will stand foremost in the rank ofsuch works, from its location as well as from its magnificent proportions. As itis calculated to last for ages, it will, in the course of time, become the greatestthoroughfare of the world, not even the London bridges excepted.

The stays which are to be employed next to the tower as an assistance to thecables in support of the bridge, will act in proportion to the sine of the angle ofinclination. The further off from the tower they reach, the less they will beable to bear. It will be necessary here to introduce those simple calculationsby which their relative strength is determined. It may be sufficient to state,that the same allowance of wire will be made for them which has been madefor the cables. It now remains to consider the strength of the suspenders.

The maximum weight of one foot of floor, and load, was rated at 3000 pounds.The greatest tension, therefore, which a suspender of 1 3-16 inch in diameterwill have to support, will be 6000 pounds. I need only remark that good char-coal iron of this size will bear 60,000 pounds, or ten times as much as the aboveweight. The reason why more strength is allowed in proportion for the sus-penders than for the cables, is because the former are sometimes subjected tosudden vibrations and shocks, which are only confined to a small portion of thefloor, and will never sensibly affect the cables.

The preceding examinations appear to authorize the conclusion, that thestrength allowed for the stays, cables, and suspenders, will prove fully adequatefor the support of the heaviest loads to which the bridge can possibly be sub-jected. But the question arises whether no other forces may be brought tobear against the cables but those resulting from transitory loads ? High windshave, in several instances, proved destructive to suspension bridges. But in allthose cases which are on record, it can be proved that the work had not sufficientstrength, and that the injury was caused by the undulations of a very flexiblefloor, the rise and fall of which produced a succession of shocks, which broke