The Board of Consulting Engineers of the East River Suspension Bridge, to connect Brooklyn with New York, have lately held several meetings to consult on the plan of the proposed structure in its details, with such results as will serve to remove many of the doubts in the minds of the unprofessional and induce them to share the confidence of the Board. The gentlemen comprising the Board are the well-known engineers, Horatio Allen, W. J. McAlpine, J. Dutton Steel, Benjamin H. Latrobe, John Serrell, J. P. Kirkwood, and J. W. Adams. They unanimously decided, after a careful and detailed examination of Mr. Roebling's plans, that there is no insurmountable obstacle to building a suspension bridge of 1,600 feet span and even much greater. The problem of a proper foundation for the towers presents the greatest difficulties. On the Brooklyn side it had been found by borings that there was a substratum of boulders which could not be disturbed by the current, and here a firm foundation could be obtained. But on the New York side the borings indicated only sand and decomposed rock, and the question was' earnestly discussed whether the current of the estuary might not, in time, wash and scour out this sand, rendering the foundation of the tower insecure. By careful comparison of old charts with the present state of the river bed the Board concluded that the narrowing of the channel by artificial encroachments while increasing the force of the current, had not materially affected the margins, nor tended to scour the New York shore. Mr. Roebling firmly believed that it would not be necessary to dig as low as 107 feet below low water mark, at which point solid rock was found, and his opinion that a depth of 70 feet would be sufficient was concurred in by the Board. On digging the foundation for the dry dock, which is near the proposed site of the New York tower, Mr. McAlpine found the sand capable of sustaining a weight of ten tuns per square foot. The weight of the bridge towers is to be only four tuns to the square foot. The area of the foundation will be 165 by 100 feet, composed of heavy timber, the mass to be 20 feet thick and securely bolted together. On this the tower, of heavy stone masonry, is to be erected, 300 feet high. On the Brooklyn side it is believed no timber substructure will be required, the masonry resting directly on the rock. The rigidity, sustaining power, and durability of the bridge were severally considered, and the plans submitted to secure each of these elements were unanimously adopted; the great work will, it is believed, be very soon commenced. The Cincinnati bridge (of which we shall shortly give an engraving and description) has a span of 1,057 feet, and the second Niagara bridge one of 1,264 feet,—336 feet less than that of the proposed East River bridge.
This article was originally published with the title "The East River Bridge"