Engineering Wonders of the World
Volume I

106 ENGINEERING WONDERS OF THE WORLD. water leaking through from the river would have been under the great pressure of 130 lbs. per square inch. But no trouble of the- sort occurred, and as a historian of the work says, “ The tunnel was so dry as to be dusty.” This tunnel is 10j feet in diameter and 1,250 feet long, lined with brick all the way. It has served the city continuously since its completion in 1888. Five years after the Croton Aqueduct Tunnel, a gas company began driving a tunnel under the East River to carry gas from its works in Long Island city to Manhattan Island, the old city of New York, and now the central part of the greater city. The location was fixed at Seventieth Street, The East River Gas Tunnel. Manhattan. The rocky shores, and the rock island (Blackwell’s Island) which hore divides the East River, gave promise that a tunnel would pass through rock uninterrupted by soft soil and water — the tunnel builder’s bugbears—and test borings seemed to confirm this. An Englishman, Mr. Charles M. Jacobs, was appointed chief engineer. It was planned to excavate a passage 10 feet by 8 feet, through which several large gas mains could be laid. Shafts were sunk on both banks, and the tunnel started outward at a depth about 100 feet below water level. But after only a few hundred feet advance both sides ran into soft ground. The two river channels, it was found, were geological “ fault ” lines, in which the nearly vertical strata of Fig. 4.—ANOTHER PHASE OF THE SURVEY WORK IN A TUNNEL. Men engaged in checking the levels, and in measuring the horizontal diameter, to note whether the pressure above has flattened the tube.