This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1895 Excerpt: ... inches up-stream from its true position, and afterwards moved down by wedging. If placed out of position down stream its adjustment is difficult. To prevent the cylindrical column from being forced upwards by air-pressure, and to insure its descent as the sinking proceeds, it is loaded until it overcomes skinfriction and other resistance, whilst yet thoroughly under control so that it may be readily hung up when necessary. If the loading is insufficient, the column may be lifted with an increase of airpressure or may fail to descend as the excavation below it is performed, in which event an inrush of drift may occur if the ground is loose. Under favourable conditions concrete loading is sufficient, but where more weight is necessary, rails or other available materials are placed...