Page:Popular Science Monthly Volume 32.djvu/165

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trated by cuts, describes this contrivance, and also another of the improvements of Couvreux. These applied, by-the-way, to the buckets and chains of dredges as well as to those of excavators.

Professor J. E. Nourse, U. S. Navy, in his report on the Suez Canal, published in 1884, says (p. 69) with reference to the French excavator:

In 1865 Couvreux invented a dry dredger which he called the excavateur chargeur. This was a dredger mounted on a car which ran on a tramway parallel with the canal. Its chains and iron buckets descended to scoop up the sand, emptying it into cars, which were themselves drawn up to the summit of the embankment along a succession of tramways.

In the above extract the method is designated by which the earth scooped up by the excavator is got rid of—that is, by means of dirt cars on common tracks. The methods by which the earth brought up by dredges was disposed of were three in number: By the first the sand was emptied into a hopper and thence conveyed through a duct, two hundred and twenty feet long, to and beyond the banks. Steam pumps injected water into the hopper, thus facilitating the discharge. Such a dredge was called a drague à long couloir. At times the banks were too high to admit of this process, and recourse was had to the second method, a mechanism called the Hevateur. It consisted of an elevated railroad, supported by iron posts, partly upon the bank and partly upon a barge between the bank and dredge. Sometimes the dirt-cars carried the earth to a height of fifty-six feet. The cars were attached to an endless chain, and passing upward along the road were emptied, and returned underneath the track. Cuts of these parts of the machinery may be found in Professor Nourse's report already referred to. The third method was the common one of barges or lighters. These were furnished with engines, and carried their contents either to lakes along the line of the canal, or near either terminus, to the sea, and were emptied by means of under- or side-doors.

While, in executing an undertaking like that at Suez, the work consists chiefly in digging, certain parts require to be built up in the proper sense of the term. It was necessary to establish upon the Mediterranean an artificial harbor, and two jetties were constructed. Here was founded the city of Port Said. In the construction of these piers we have an example of the way in which the adversaries of the undertaking asserted, without any sufficient basis, the impracticability of the work. The "Edinburgh Review," referring to the construction of the jetties, said: "Any constructions attempted so as to form an entrance for the canal will be swallowed up. Every block, every stone, will be swallowed up, and we shall not see a single one above water." Mr. Fitzgerald quotes this passage. Referring in particular to the western pier, supposed to be specially difficult of construction, because it was to arrest large bodies of sand moving at this.