Worthen, William Ezra, 1819-1897, [from old catalog] ed · New York, Appleton · leaf 449
Fig. 1028. Fig. 1029. Mr. McAlpine enlarged the bottom of the cylinder to a conical form, andalso added largely to the bearing surface by poling-boards driven obliquely out-ward. After the excavation was completed, a strong course of concrete waslaid, and, when set, the air-lock was taken off and…
Mechanical drawing
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