Spon's dictionary of engineering, civil, mechnical, 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. 1880 Excerpt: ...so that the filling in could bo accomplished more easily. The cutting edge is always strengthened by additional plates. At Lorient the thickness was 2T'j in., with several plates stepped back so as to form a sort of edge; the sides were about in. thick at the bottom, and-fa in. at the top, and the roof was curved a little to increase its strength. At Vichy the plates were about in. thick. At La Voulta, Hollandsch Diep, ami Lucerne, a sort of masonry lining was placed against the iron plates, and kept in place by gusset plates, to afford greater rigidity against tue pressure of the earth. At St. Maurice, wooden struts were put in at the base of the caisson, and also halfway up to support the sides. In consequence of these modifications, the caisson at Lucerne, 55 ft. by 13 ft., weighed only 28 tons; the caisson at St. Maurice, 32 ft. by Hi ft., weighed 14 tons; whereas at Kehl, a caisson 23ft. by 19 ft. weighed 34 tons, at Lorient, 39$ ft. by Hi ft. weighed 27$ tons, and at Riga, 64$ ft. by IB ft. weighed 45$ tons. The height of the chamber of excavation sheuld be about 8 ft. 10 in. Frequently the cofferdam casing is of iron, which protects the newly built masonry from friction; ana the upper portion of the casing can bo removed. At Lorient there were two air locks, Figs. 531, 532, each connected with two shafts, in which bulanced skips went up and down. On the top of the bottom caisson a casing of sheet 531. iron, from-fg to i in. thick, and weighing about 15 tons, was erected in successive rings. The Americans have ndoptt d the pnenmatic system for some large works and introduced improvements. At the St. Louis Bridge the foundations were carried to a greater depth than had been previously attained; and at the East River Bridge, New York, compressed air was...