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BURROWING UNDER NEW YORK'S RIVERS
These human moles face, fight, and conquer difficulties in respect to their working conditions in laying
a tunnel that seem beyond man's capabilities. The photograph below shows one of the caissons start­
ing down. Note its heavy construction and the beginnings of the openings through which the shields
will be pushed. The upper photograph was snapped in the compressed air chamber of the same caisson.
The pressure here was forty-four pounds to the square inch—very near to the legal limit, which is fifty
pounds maximum in New York State. Workers can stay in this pressure only forty-five minutes at a
stretch, after which they are compelled to spend over half an hour in the recompression chambers, getting
back to normal, before they can rest.