Dodge, Mary Mapes, 1830-1905 · [New York : Scribner & Co.] · leaf 436
o the soft earth above, anddug out an upper heading. This was done with-out a shield and compressed air by carefully tim-bering the work as is shown below in Figure i.For, because the earth was of a clayey nature, itwas not so necessary to guard against beingswamped with water. However, at one… … FIGURE I. CUTTING THROUGH ROCK AND EARTH. tunnels to form an air-lock. After the dangerhad been passed, the doors of the air-lock wereremoved, but the concrete bulkheads were left inplace for use again, if needed. On Sundays no work was done at the tunnels,except possibly some repairs to the…
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