nized wire will be used. Near the saddle, where the wrapping machine cannot be placed, the cable is bound together with iron bands about five inches apart. At the point in the anchorage, whence the different strands diverge, a heavy iron ring in addition must be placed, in order to lessen the strain on the wrapping wire. The single strands are wrapped. by hand from this ring close to the shoe. Immediately after having wrapped the cable for a certain distance, it should be painted with several coats of good oil paint, so that the little spaces between the wires are completely filled up, giving to the cable a smooth cylindrical appearance and preventing the moisture to penetrate. This operation finishes the cables, which are now ready to receive the superstructure. This should be put on symmetrically to the towers, and simultaneously in centre and land spans, in order to avoid uneven tension in the cable, and strain on the towers. After the greater part is suspended, the blocking, which held the saddles in place, is removed, giving to the cable free chance to move back or forth, and to assume its natural position of balance. We have shown that under a certain temperature, this motion will be about two inches towards the river. The temperature under which the first strand of the East River bridge cable was regulated, happened to be 75-80° F. If the saddle blocking is removed on a colder day, the above motion will be less owing to the greater tension in the land cable, caused by greater contractions, than the river cable. The reverse will take place if the saddles are set free on a warmer day. Condition, however, always is that in each span the weight of the superstructure is the same, and symmetrical to the tower. The lengths of the suspenders must be calculated according to the final curve of the cable, which is attained when the stays are put in place. Before this the floor will have an irregular shape, provided all suspenders have their exact the stays length. A continuous grade of the floor will, however, be established as soon as are put under tension, which will cause the cable to assume that curve for which the suspenders were calculated, bringing thereby, the latter also under their proper tension. Errata.-Page 61, in Fig. 27, add to point M the denomination I. Page 66, fifth line from above, instead of λ, read: 1. Page 70, sixth line from below, instead of I, II, read: II, III. Page 71, twelfth line from above, instead of 14500-w, read: 14500×w. Any book in this Catalogue sent free by mail, on receipt of price. VALUABLE SCIENTIFIC BOOKS, PUBLISHED BY D. VAN NOSTRAND, 23 Murray Street, and 27 Warren Street, NEW YORK. WEISBACH. A MANUAL OF THEORETICAL MECHANICS. By Julius Weisbach, Ph. D. Translated by Eckley B. Coxe, A.M., M.E. 1100 pages and 902 wood-cut illustrations. 8vo, cloth, FRANCIS. LOWELL HYDRAULIC EXPERIMENTS-being a Selection from Experiments on Hydraulic Motors, on the Flow 01 Water over Weirs, and in open Canals of Uniform Rectangular Section, made at Lowell, Mass. By J. B. Francis, Civil Engineer. Third edition, revised and enlarged, with 23 copper-plates, beautifully engraved, and about 100 new pages of text. 4to, cloth, KIRKWOOD. ON THE FILTRATION OF RIVER WATERS, for the Supply of Cities, as practised in Europe. By James P. Kirkwood. Illustrated by 30 double-plate engravings. 4to, cloth $10 00 15 00 15 00 |