Under the Hudson

Through solid rock, shifting sand, sliding mud, two great shields are boring toward each other under the Hudson River. When they have come together there will be a new vehicular tunnel from Manhattan to New Jersey. The moment of their marriage is, for the engineers in charge, the zero hour. The latter will not know till then whether they have calculated perfectly this blind meeting underground or whether their plans have gone awry.

Last week the shields were less than 500 ft. apart. In spite of their huge weight, the distance they have been propelled, and the many difficulties, Chief Engineer Clifford Holland and his staff were confident that the calculations will not be wrong by more than an inch. Each shield weighs 400 tons. The one from New Jersey has taken a snake-like course through mud, the one from Manhattan has had to eat through stone. They move in shoves of 2 1/2 ft.; and after each shove, "sand hogs" probe for obstructions with long iron bars. Manhattan skyscrapers are used as observation points on which the lines of progress are sighted. Completion of the tunnel is predicted for October.