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Page:Popular Science Monthly Volume 32.djvu/164

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152
THE POPULAR SCIENCE MONTHLY.
These inventions show the admirable fertility of resource that regulates the work of foreign engineers, who devise machinery to suit the difficulties of each stupendous work; whereas in this country (England) the objection is often, made to such undertakings, that engineering does not furnish means to accomplish them. However this may be, the Mont Cenis Tunnel and Suez Canal are excellent instances in point, the difficulties themselves prompting the discovery of means to overcome them.

For a detailed description of the Suez dredges and their appurtenances, Mr. Fitzgerald's work may be consulted, vol. i, pages 203212. Here we shall only give an account of the principles involved and certain particulars, in which these mechanisms were in advance of preceding ones. The great dredges and excavators employed at Panama go back for their origin to this period. In 1860 an invention was brought out by two engineers, Cavé and Claparède, to facilitate the excavation of canals and cuttings upon railroads. They proposed to use a series of scoops or buckets attached to a revolving, endless chain, and to apply this device both to the ordinary dredge, and to a machine, constructed for the purpose, to be used in dry excavation. This was the origin of the present chain-of-buckets dredge and chain of-buckets excavator.[1] The latter machine was first used in France in 1860 upon the Ardennes Railroad, between Sedan and Thionville. In an article in "Le Génie Industriel" for December, 1860, containing cuts of the chain-dredge and chain-excavator, it is said: "Such machines may, above all, be applied to the work on the Suez Canal. They will allow of the reduction in a notable manner of hand-labor, and, in consequence, economize a considerable part of the expense."

This statement was written about eighteen months after work on the Suez Canal was begun; just what the writer anticipated occurred. By one of the contractors, Lavalley, the principle of Claparède was successfully applied to dredges; and the Claparède excavator was in like manner improved by another of the contractors, Couvreux, who built what is called the excavateur Couvreux. He took a contract for excavating the seuil d'El Guisr, a ridge which crosses the line of the canal for a space of ten miles, its highest points being sixty-five feet above the sea. This work was finished six months inside the contract time, a result to be ascribed in part to the Couvreux excavator.

One of the improvements introduced by Couvreux consisted in inserting movable bottoms in the buckets. In clayey and adhesive soils the buckets sometimes clogged, so that much time was required to clear them. By the new arrangement the bottom was forced forward, and the clearance thus effected. The bucket having descended, a fresh load of earth drove the bottom into its original place. An article in "La Propagation Industrielle" for September 1, 1868, illus-

  1. This principle, it is true (the use of the endless chain), was applied to a certain extent in the case of dredging, both in France and England, early in the century. (See Knight's "American Mechanical Dictionary," vol. i, pp. 747, 748.)