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THE POPULAR SCIENCE MONTHLY.
that two single-track tunnels would be cheaper, and one of them would sooner be available for traffic. Experience has proved that a second tunnel will not be required for a long time. The largest number of freight cars passed through in twenty-four hours
Fig. 4.—Section of the Tunnel and River-bed.
during the two years the tunnel has been in use was one thousand and fifteen, while twenty-five hundred could be handled if occasion required. The average number is seven hundred in
