ACCIDENT AT THE CENTRAL SHAFT. 509 charges of nitro-glycerine in long tin tubes. These were put in the holes, the wires were fastened in their places, and then the men moved back; it is hardly necessary to say that I moved back at the same time, and quite as far as the workmen. Everything being ready, the signal was given. "Look out that you are not blown down!" said my guide. I did look out. There came a sound and a quick explosion, followed by the rumbling and crashing of the rock, and then a rush of air and smoke that almost threw me over. The pressure of the air in the iron pipe for working the drills and ventilating the tunnel was about six atmospheres, or ninety pounds to the square inch. As soon as the blast was made, the air was turned on; the smoke from the blast was driven back, and the miners found themselves in a clear atmosphere. After this blast it was intimated that there was nothing more to see, and we made our way out of the tunnel into the open air again, and back to the Wilson House. On December 12th, 1872, the east heading was connected with the one driven east from the central shaft. The west heading was connected with the one driven west from the shaft on the 27th of November, 1873. This proved a splendid engineering feat. The road bed was finished and the track laid early in 1875, and the first freight train passed through on the 5th of April of that year. The first passenger train was run through, July 8th, 1875. Owing to the explosive action of nitro-glycerine the rock was broken for some distance beyond the limits planned in constructing the sides and arch of the tunnel, and there was constant danger of pieces of rock falling upon the track. The plan of arching it with brick was conceived of, and a contract was made in 1874, to do the arching and also to enlarge a portion of the tunnel at the castern terminus. This work was completed, and the road is now in complete running order. The cost of the work in the aggregate is nearly $15,000,000. The construction of the tunnel opens direct communication between Boston and Troy, and is of inestimable advantage to Massachusetts from a commercial point of view. THE MONT CENIS TUNNEL. MOUNTAIN CHAINS BETWEEN NATIONS. — MONT CENIS. CROSSING THE ALPS. -THE GREAT ALPINE TUNNEL. LAYING OUT THE WORK. THE ARC AND DORA. DIFFICULTIES. THE SURVEYS. PENETRATING THE MOUNTAIN. — COMPLETION OF THE WORK. THE CHANNEL TUNNEL. ITS COST. COST OF TUNNELS IN VARIOUS COUNTRIES. IT has been said with truth that "mountains interposed make enemies of nations." In various parts of the world we find that mountain chains stand as barriers between different nations, and in many instances the boundaries thus formed by nature have remained unchanged for hundreds of years. the map of Europe the most prominent mountain chain is that of the Alps, and it has stood as a separating line between nations for a long time. It is true that occasionally wars have been carried beyond these mountain chains, and conquests have been made in spite of them; but for practical purposes the chain of the Alps has been for centuries the separating line between France and Austria on the north, and Italy on the south. Sometimes the French possessions have extended to the south of the Alps, and sometimes Italy has extended her possessions to the north of that chain. Such possessions have never been held for a great length of time, and in one way or another they have fallen to the nation to whom they belonged by natural position. Carriage roads were long since made across the Alps. In later years the railway has traversed these mountains, but the ascent is tedious and laborious, so that rapid communication was impossible. It remained for the science of the present day to overcome the obstacles which the mountains afforded, not by cutting away the Alps, but by piercing a passage through them. COMMENCEMENT OF THE WORK. 511 More than twenty years ago the attention of the French and Italian governments was called to the necessity of a tunnel through the Alps by which France and Italy should be connected. The project was discussed for some time, and finally a convention was formed between France and Italy for the purpose of undertaking the work. Four or five years were consumed in surveys and in the contemplation of plans. All sorts of objections were made, and a list of these objections forms a humorous page. One man contended that the heat would be so great in the centre of the mountain that the men would be roasted alive while working in the tunnel. Another was positive that the noxious gases and vapors arising in the tunnel would suffocate everybody. Another contended that rivers of water would be found in the mountain so great that they would overwhelm the workmen, and convert the tunnel into an enormous spring. And so on, one after another, the objections were heaped up, and there was at one time a prospect that the work would not be undertaken. The actual work on the tunnel was begun on the Italian side in 1857, and a little afterwards work on the French side also commenced. A great deal of labor had been performed in locating the tunnel. A mountain chain is not a single line of mountains, like a row of potato hills; but it consists of a central back-bone of mountains, with other and smaller mountains on either side, so that a chain may often be a hundred or more miles in width. Now, in piercing a chain like the Alps, it is necessary to find a way among the outlying hills on each. side through the valleys of the rivers that flow from the central chain. In this way the open-air railway is brought to the foot of one of the mountains forming the great central back-bone. But a difficulty arises in finding two of these valleys directly opposite each other. You may follow a valley until you get to the very base of one of the highest mountains of the range, but on looking to the other side you may find no corresponding valley. It was this peculiarity of all mountain chains that greatly |