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548 ILLUSTRATED WORLD<br />

SINKING THE HARLEM RIVER SUBWAY TUNNELS<br />

This was the first time in engineering annals that the method of sinking the cast-iron cylinders into the<br />

prepared river bed was used. After beingfloated into position they were lowered by decreasing the pressure<br />

in the air tanks. Below is a photograph showing a shield and the erector placing a section of tunnel<br />

lining. The rings are built of flanged segments bolted together to form a circle. The circular rings are<br />

bolted together to form the tunnel lining, and rendered watertight by lead caulking and grouting.<br />

». *. 3'^-<br />

,<br />

w<br />

V<br />

" m\

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