The Brooklyn Bridge

The engineers who aro suporintcnding the constiuctiou of the groat Kast liiver bridge are pushing tho work as fast as their facilities will jíermit. Nothing can be done toward strotchiiig the cables which are to form tho span until the towers are completod. As inany men as can work on the towers with comfort or safoty are employed, and the blocks of granite are piled up at the rate of two courses in three weeks. In ton weeks the Brookiyn tower will be finished, and Col. Payne, who has charge of the work on the New York tower, says that by the middle of November, when work must ceaso because of cold weathor, he will have raised the masonry to a point abovo the spring of the arches, and the wooden tratne-work for the arches can be fixed in the winter. By tho end of another soason this tower will be rinished, as well as the anchorage on both sides, leaving the cables to be strung and the bridge finished some time in the sumuier 01 fall of 1877. The New York tower is completed to a point 150 feet above high tide, while that on on the Brookiyn side is 243 feet high. The Brookiyn anchorage has been carried 40 feet abovo tide-water, and is to be nearly completed this fall. Work has not been begun on the New York anchorage, nQ,r has the land on which to build it been purchased. The managers say that they have money enough in the treasury to carry on all tho work that can be dono this fall, and that they will not want until spring the $2,000,000 which the city of Brookiyn, through the Common Council, has voted toward the project. The enginoers laugh at Mayor Havemeyer's notion that the bridge cannot be completed without building a third pier or tower in the middle of the river, and in explaining what they cali the absurdity of this theory, compare the East River bridge with other structures of a similar nature. The suspension bridge across the Ohio at Cincinnati has a total length of 2,220 feet, and a olear span between towers of 1,057 feet. It is 103 feet above low water. The roadway is supported by two wire cables, which are but 12 1-2 inches in diameter. The East Eiver bridge is to have a total length of 3,425 feet and a span of 1,595. The roadway is to be supported by four galvanized steel cables, each 16 inches in diameter. The wire has a strength of 160,000 pounds per square inch of section, the aggregate strength of the span being over 5,000 tons. These cables will be composed of steel wires laid straight like a bundie of rods, thus making the cabe stronger than it would be were it composed of twisted wire. In twisted wire cables it is iinpossible to exert the same tensión on every wire used, and some are thus made stronger than others. One of the nicest of the engineering feats in connection with the great bridge, is to be in laying these wires so that all shall have an equal tensión, and this is why an entire season, and possibly two seasons, will be required to perfect the cable-making. It cannot be done while the wind is blowing briskly, or in extremes of temperature, as heat or cold might occasion iueqnality of tensión. The cables of the East liiver bridge will be much stronger in proportion to their size than those of the Cincinnati bridge, as well as being much largor and doublé the nuinber. The difference infthe leugth of spans of the two bridges will be but 538 feet, and to overeóme this the precaution has been taken to build the Brookiyn structure at least three times as strong. The span of the Niágara Suspension Bridge is 281 feet, and the support consists of 14,560 wires. An ordinary railway train crossing it causes a depression of but or four inches. The latest estímate of the total cost of the Brookiyn bridge, as made by the engineers, iucluding land and approaches, is $13,045,065 67. Frora this sum, however, is to be taken a considerable amount for land which will be under the approaches to tho towers, and which can be utilized. The prevailing opinión that the Brookiyn bridge wheu completed will be the longest suspension bridge in the world seem8 to be erroneous, if Murray's Fndbook of France is to believed, for in it is mentioned a suspension structure crossing the Dordogne at Cubsac, and having a singlo span, between abutments, of 1,640 feet. In other respects, howover, the French bridge is far inferior to the Brookiyn bridge. This fact may be of interest to some nervous persons who have feared that the East liiver structure, when completed, might fall of its own weight, or be parted asunder by wind. A still greater project is that of the proposed suspension bridge across the Hudson River at Anthony's Nose, four miles froni Peekskill, which according to Engineer Serrell, is to be 1,665 feet long between the towers, and is to be suspended 155 feet above the water. This project is, however, in its infancy.