Engineering Wonders of the World
Volume I

108 ENGINEERING WONDERS OF THE WORLD. lished, and the tunnel was visited by crabs and mussels, together with boulders, old boots and shoes, brick and tinware, direct from the river bottom. Notwithstanding these adverse circumstances, the work was still progressing, though in 45 lbs. of com- pressed air. On December 13, 1893, the Fig. 7.—SECTIONAL VIEW OF HUDSON RIVER SHIELD, SHOWING PROJECTING ROOF FOR PROTECTING WORK- MEN WHILE BLASTING OUT A REEF OF ROCK. {By courtesy of the “Scientific American.”) shield finally cleared the rock, and was fully entered into the mud. The main difficulty was now surmounted, the work progressed more rapidly, and the shield soon reached undisturbed material, which was found to be quite dry and hard. Mattocks were used in the working chambers by the men, who would clean out these four compart- ments to within a foot of the cutting edge. As soon as this was done hydraulic pressure was put on the jacks, sometimes to the amount of 5,000 lbs. per square inch, and the shield forced ahead 16 or 18 inches, enough for another ring of plates, the work- ing chambers again being filled with the displaced material. On December 24 the last of the black mud was passed through. On January 16, 1894, the end of the soft seam was reached with the shield, and rock was again entered, after having passed through 98 feet of soft ground.” The tunnel was completed late in 1894. Most of its length was in rock, and the shields of both sides were taken out as soon as the soft ground was safely passed. Of the tunnel’s whole length of 2,516 feet—half a mile—all but some 400 feet was a simple, uneventful piece of rock tunnelling. The great expense of the shield and compressed air had to be incurred merely to make possible the passage through four 50-foot seams of soft soil. The East River Gas Tunnel is notable for the highest air pressures ever used .in Ameri- can tunnelling: 48 and 50 lbs. per square inch were carried at times. With such enormous pressures—working becomes danger- ous at 30 lbs.—fatal cases of “ bends ” can hardly be avoided, and here, in spite of the short duration of the pneumatic work (barely five months), there wer© four deaths from the effects of the air. Since that period, more careful medical inspection and regular use of the “ hospital lock ” (Fig. 5) have much reduced the mortality. THE HUDSON TUNNELS OF THE HUDSON AND MANHATTAN RAILWAY COMPANY. The great 170,000,000 Hudson and Man- hattan Railway system began as long ago as 1873, but in a very different scheme. A bold enthusiast, D. C. Haskin, conceived the idea of tunnelling under the Hudson so as to bring directly into New York all the railways terminating on the New Jersey shore. He thought .that shields were unnecessary, and that compressed air alone would enable him to construct his tunnel even in the treacherous river mud. He even undertook the work as a