Engineering Wonders of the World
Volume III

THE GREAT TUNNELS THROUGH THE ALPS. 149 maintained the kindlier traffic of commerce. Splendid roads were constructed over the passes by military engineers—by the Romans first, and, many centuries later, by the great Napoleon. Early in last century regular stage-coach services were established, and, except in winter, served the needs of the comparatively small travelling public. Presently came the development of the rail- way. Tracks crept up from all points of the compass, but on reaching the Alpine slopes had in most cases to stop The Semmer- a^rUp^y The first line to ing Railway. cross the Alps was the bem- mering Railway, which in the years 1848-54 was led over the Semmering Pass, to open direct communication between Vienna and Austria’s greatest seaport, Trieste. The Sem- mering Pass lies in one of the Alpine offshoots. At the crest a tunnel had to be driven through nearly a mile of rock ; otherwise the work was confined to bridging, cutting, and filling. Soon after the completion of this enterprise the French began to busy themselves with a much more ambitious project—that of piercing the Col de Fréjus, about 18 The Mont miies south of Mont Cenis, with Cems Tunnel. . a double-track tunnel, nearly eight miles long, which should be the last link in the Victor Emmanuel Railway, and bring Paris within eighteen hours of Turin by rail. At that time trains ran on the French side to Modane, whence passengers and baggage had to be taken fifty miles by road—later, by the Fell surface railway—over the mountains to the terminus, at Susa, of the railway on the Italian side. An agreement was made between the French and Italian Governments whereby the latter undertook the financing of the work, but sub- let the driving of the western half of the tunnel to the French for £760,000, plus a premium of £20,000 for every year less than twenty-five years, and £24,000 for every year under fifteen years saved in construction. The French Government agreed to pay a sub- vention of £800,000 as their share. Great public interest was aroused by the boldness of the scheme. A tunnel of so great a length had not been attempted previously in any part of the world. The difficulties ahead could not be Gigantic Undertaking. estimated, owing to the lack of experience in burrowing under lofty moun- tain peaks. As it would be impossible to sink air-shafts along the line of the tunnel, serious problems of ventilation had to be faced. At that period, moreover, gunpowder was the only blasting agent available. To sum up, the ample time limit—twenty-five years—allowed by the contracts affords suffi- cient proof that the driving of the Mont Cenis Tunnel was regarded as a very formidable task. At first boring proceeded very slowly in- deed, and at the end of five and a half years only one-fifth of the work had been accom- plished. The introduction of a -n i The Mountain the Sommeiller compressed-air K pierced. drill expedited matters, how- ever, and seven and a half years more sufficed for completion. On Christmas Day, 1870, at 4.25 p.m., drill No. 45, working on the Italian side, knocked a bore-hole 12 feet long through the barrier of rock separating the advanced galleries driven by the French and Italian gangs. The information was telegraphed to Turin, and contractors and engineers hurried up on a special train. Meanwhile a number of bore-holes were made in the rock curtain and filled with, blasting charges. When the last were fired the galleries were brought into communication ; and at 5.30 p.m., on Decem- ber 26, M. Copello, the engineer in charge of the works on the French side, passed from end to end of the tunnel, entering at Modane and coming out at Bardonneche, the Italian portal. The error in direction was found to be nil, the vertical error to be one foot, and the actual length to be 15 feet in excess of