... rock, which in some places lies covered with mud 100 ft. or more below coping level. Compressed air is used to work the sliding caissons which close the entrances of the docks and closed basin. A ropery at Devonport produces half the hempen ... — Encyclopaedia Britannica, 11th Edition, Volume 8, Slice 3 - "Destructors" to "Diameter" • Various
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