BORING MACHINES USED IN MOUNT CENIS TUNNEL, THE ALPS.—THE LARGEST TUNNEL IN THE WORLD, CONNECTING FRANCE AND ITALY.
With the exception that the workmen were clad in different costumes, and were shouting in French instead of English, the work was very much like that already described in the Hoosac Tunnel. Accidents were much more frequent in the Mont Cenis Tunnel than in the Hoosac Tunnel, for the reason that much less care was taken. It was said that nearly twelve hundred men lost their lives in the tunnel, or in connection with it, during the time of its construction,—at least, some of the workmen said so,—while the guides and directors insisted that the loss of life had not been more than one tenth of the number. Owing to the hardness of the rock the cost of the work was very great. Taking the average of the whole length of the tunnel, it was one thousand dollars a lineal yard, making a total, in round numbers, of fifteen millions of dollars.
The expense was shared between the French and Italian governments, and the tunnel will form a bond of union between the two nations greater than could be made by any other use of the same amount of money. By the terms of the convention between the governments, the tunnel is to remain uninjured should France and Italy be engaged in hostilities against each other. The tunnel shortens the route of travel very materially, and where the route of travel is shortened the work of peace and good will among men is greatly facilitated.
TUNNEL UNDER THE ENGLISH CHANNEL.
A tunnel has been proposed for the Straits of Dover, between England and France, and several plans have been considered. The London Times stated, early in 1872, that a company has been formed and funds subscribed to the amount of some one hundred and fifty thousand pounds, with the immediate object of making a trial shaft, and driving a driftway on the English side about half a mile beyond low-water mark, with the view of proving the practicability of tunnelling under the Channel. The completion of this work will furnish data for calculating the cost of continuing the driftway from each shore to a junction in mid-channel, and capital will then be subscribed for that purpose, or for enlarging it to the size of an ordinary railway tunnel, as the engineers may deem most expedient.
The tunnel will be made through the lower or gray chalk chiefly, if not entirely, and by the adoption of machinery, of which the promoters of this company have recently made practical trials, it is expected the passage from shore to shore can be opened within three years from the time of commencing the work, and at a cost very considerably less than any previous estimates.
COST OF TUNNELS.
The same paper, referring to the proposed enterprise, gives the following details about railway and other tunnels: “The cost of existing tunnels has been governed by such various conditions of locality and soil, that they can have little bearing upon the present question. It may be worth while, nevertheless, to cite a few prominent examples. The Mont Cenis Tunnel has cost one hundred and ninety-five pounds per linear yard, which would amount, for a length of twenty-two miles, to seven millions four hundred and fifty thousand four hundred pounds. The three most costly tunnels made in England have been the Kilsby, the Saltwood, and the Bletchingley, each of which was executed in treacherous strata, giving out large quantities of water. In making the Kilsby Tunnel a hidden quicksand was discovered, by which the works were drowned out. For a considerable time all pumping apparatus appeared insufficient, but by the employment of one thousand two hundred and fifty men, two hundred horses, and thirteen steam engines, working night and day for eight months, one thousand eight hundred gallons per minute were raised from the quicksand alone. The cost of the work was raised from ninety thousand pounds, the original estimate, to three hundred and fifty thousand pounds, or one hundred and forty-five pounds per yard for two thousand four hundred yards. The same rate of expense for twenty-two miles would amount to five millions six hundred and forty-six thousand six hundred and twenty pounds. The Saltwood Tunnel cost one hundred and eighteen pounds per yard, the Bletchingley seventy-two pounds; or for twenty-two miles, four millions five hundred and sixty-eight thousand nine hundred and sixty pounds, and two millions seven hundred and eighty-seven thousand eight hundred and forty pounds, respectively.
“The cost of railway tunnels in France has varied from thirty pounds per yard—being that of Terre Noire, on the Paris, Lyons, and Mediterranean Railway, to ninety-five pounds per yard, that of Batignolles, near Paris, on the Chemin de Fer de l’Ouest. In Belgium, Braine le Comte Tunnel cost forty-six pounds per metre, and the tunnels on the Liège and Verviers line fifty pounds per metre. In Switzerland the very difficult Hauenstein Tunnel between Basle and Berne cost eighty pounds a yard.