Supplement to Spons dictionary of engineering, civil, mechanical, military, and naval Volume 1

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. 1879 Excerpt: ...three equal parts by timber beams C C, running in u direction at right angles to that of the iron girders above the roof. Inset picces of plate iron are connected to these beams nt intervals, to stiffen and support the roof. The bottom of the eaisson projects a couple of feet below the timber beams and sills, so as to form a cutting edge. The sand was foreed up by a pressure of w.iter amounting to 150 lb. the sq. in. One pump, having a bore of 3£ in., lifted 20 cub. yds. to a height of 125 ft. an heur. The masonry inside. Fig. 533, was built up as tho eaisson sank upon the air chamber. When the rock was reached, the shafts and the air chamber below were filled with concrete, and thus becoming one solid mass, constituted the real foundation or basis of the permanent structure. The eaisson, H H, of plate iron » in. in thickness, was removed to be used again as required. Fig. 534 represents the plant employed in laying the masonry and sinking the eaisson. A A are the dick irons on the pontoons BB, FF hydraulic jacks for raising materials, K wire eable for supporting travelling purehases, M M shatts for starting and stopping the same, N N valve hydraulic jacks for raising and lowering materials, O air pumps nnd t ngines, Q hese for supplying air, SS serews for keeping the caisson level befoie reaching the sand, W W guide piles ftj eaisson X, Z Z truss, s for guide piles. It will be seen that a numb,r of wrought-iron piles, about 3ft. 6in. diameter. are arranged round the eaisson, and that thise earry upon the framework they support a set of screws, each 25 ft. long, for maintaiaing the level of the eaisson until the smd is reached. On the outside of the guide-piles aro placed two pontoons, earrying double jibs, which project on one side over the flats...