CENTS, se-ne, Mont, a mountain belong ing to the Graian Alps, between Savoy and Piedmont, 11,755 feet high. It is famous for the winding road nearly 40 miles in length constructed in 1803-10 by Napoleon I, which leads over it from France to Italy, and for an immense railway tunnel, which required nearly 14 years' labor. It superseded a grip railway which was constructed over the moun tain by Mr. Fell, an English engineer, in 1864 68. The tunnel does not actually pass through the mountain, but through the Col de Frejus, about 15 miles to the southwest. The Mont Cenis Pass is 6,765 feet above the level of the sea, whereas the elevation of the entrance to the tunnel on the side of Savoy is only 3,801 feet, and that on the side of Piedmont 4,246 feet. The total length of the tunnel is 42,145 feet, or nearly eight miles. For the sake of the drainage the bottom of the tunnel has a culminating point about the middle, and falls southward 128 feet, and northward 473 feet. The breadth of the tunnel at the base is about 25 feet, at the widest part about 26 feet; its height at the Modane end is 24 feet 7 inches; at the other end about a foot higher. The de termination of the exact direction and height of the tunnel occupied a full year, and the work of piercing the tunnel was carried out with so much precision that the borers who had begun simultaneously from both ends met exactly. The tunnel is laid out for two lines
of railway. The roof and walls are lined with masonry to the thickness of two feet seven inches, and where the ground is not very firm it is underarched. The boring was at first car ried on by hand labor, and one-eighth of the total length of the tunnel was finished in this way, but the rest was constructed by machines specially devised for the purpose. Each boring machine had 18 borers, by which holes about three feet in depth were wrought in the rock. For the blasting of every yard of the tunnel 97 borings on an average had to be made, and above 100 pounds of gunpowder were employed. The total cost of the tunnel amounted to $14, 475,000, which was borne partly by the French and Italian governments and partly by the Northern Railway Company of Italy. The first mine of the tunnel on the Italian side was exploded by Victor Emmanuel at the end of August 1857; on Christmas Day, 1870, the workmen met in the middle of the tunnel; and on 17 Sept. 1871, the tunnel was officially opened. See TUNNELS.