. The Encyclopaedia Britannica; ... A dictionary of arts, sciences and general literature. er called an air-lock at the upper part This air-lock serves for the exit and entrance of the workmen and materials; the air in this compara-tively small space • is lowered to the pressure of the atmosphere before the chamber is opened for the passage of men or materials to the open air ; the air is again compressed in the air-lock before it is opened for communication with the body of the shell in which the air is permanently kept at such a pressure as will keep the water down to the required leveL The
. The Encyclopaedia Britannica; ... A dictionary of arts, sciences and general literature. er called an air-lock at the upper part This air-lock serves for the exit and entrance of the workmen and materials; the air in this compara-tively small space • is lowered to the pressure of the atmosphere before the chamber is opened for the passage of men or materials to the open air ; the air is again compressed in the air-lock before it is opened for communication with the body of the shell in which the air is permanently kept at such a pressure as will keep the water down to the required leveL The shell thus acts as a diving bell acts. It is found that men cannot in general be safely employed under a greater pressure than two atmo-spheres above-the ordinary atmospheric pressure, cor-responding to a depth in water of about 65 feet. The centre pier of Saltash Bridge was, however, in 1855 by this plan carried down to a depth of 87 feet 6 inches below high water. Recently the foundations of St Louis bridge over the Mississippi have by the same method besn established at a depth tJ. Fig. 96.—Cylinder, caiaringCrosaBridge. SUBSIKUCTURE.] B K I D G E S 327
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectencyclo, bookyear1902
