THE TUNNEL THROUGH MONT CENIS.

Star (Christchurch), Issue 241, 19 February 1869, Page 3

THE TUNNEL THROUGH MONT CENIS.

(Daily News.) Men flash their messages . across mighty continents and beneath the bosom of the wide Atlantic; they -weigh the distant planets, and analyse the sun and stars ; they span Niagara with a railway bridge, and pierce the Alps with a railway tunnel ; yet the poet of the age in which all these things are done or doing sings, " We men are a puny race." And, certainly, the great works which belong to man as a race can no more be held to evidence the importance of the individual man than the vast coral reefs and atolls of the Pacific can be held to evidence the working power of the individual coral polype. But if man, standing alone, is weak, man working according to the law assigned to his race from the beginning— that is, In fellowship with his kind— is, indeed, a being of power, , Perhaps no work ever undertaken by men strikes one as more daring than the attempt to pierce the Alps with a tunnel. Nature seems to have upreared these mighty barriers as if with the design of showing man how weak he is in her presence. Even the armies of Hannibal and Napoleon seemed all but powerless in the face of those vast natural fastnesses. Compelled to creep slowly and cautiously along the difficult and narrow ways which alone Svere open to them, decimated by the chilling blasts which swept the face of the rugged mountain-range, and dreading at every moment the pitiless swoop of the avalanche, the French and Carthaginian troops exhibited little of the pomp and dignity which we are apt to associate with the operations of warlike armies. Had the denizen of some other planet been able to watch their progress, he might, indeed, have Baid, " These men are a puny race," In this only, that they succeeded, did the troops of Hannibal and Napoleon assert the dignity of the human race. Grand as was the aspect of nature, and mean as was that of man during the progress of the contest, it was nature that was conquered— man that overcame. And now man has entered on a new conflict with nature in the gloomy fastnesses of the Alps. The barrier which he had scaled of old he has now undertaken to pierce. And the work— bold and daring as it seemed — is three parts finished. The Mont Cenis tunnel was sanctioned by the Sardinian Government in 1857, and arrangements were made for fixing the perforating machinery in the years 1858 and 1859. But the work was not actually commenced until November, 1860. The tunnel, which will be fully seven and a half miles in length, was to be completed in twenty-five years. The entrance to the tunnel on the side of France is near the little village of Fourneau, and lies 3,946 feet above the level of the sea. The entrance on the side of Italy is in a deep valley at Bardoneche, and lies 4,380 feet above the sea-level. Thus there is a difference of level of 434 feet. But the tunnel will actually rise 445 feet above the level of the French end, attaining this height at a distance of about four miles from that extremity ; in the remaining three and threequarter miles there will be a fall of only ten feet, so that this part of the line will be practically level. The rocks through which the excavations have been made have been for the most part very difficult to work. Those who imagine that the great mass of our mountain-ranges consists of such granite as is made use of in our buildings, and is uniform in texture and hardness, greatly underrate the difficulties with which the engineers of this gigantic work have had to contend. A large part of the rock consists of a crystallized calcareous schist, much broken and contorted; and through this rock run in every direction large masses of pure quartz. It will be conceived how difficult the work has been of piercing through so diversified a substance as this The perforating machines are calculated to work best when the resistance is uniform; and it has often happened that the unequal resistance offered to the perforaters has resulted in injury to the chisels. But before the work of perforating began, enormous difficulties had to be contended with. It will be understood that, in a tunnel of such vast length, it was absolutely necessary that the perforating processes carried on from the two ends should be directed with the most perfect accuracy. It has often happened in short tunnels that a want of perfect coincidence has existed between the two halves of the work, and the tunriellers from one end have sometimes altogether failed to meet those from the other. But in

a short tunnel this want of coincidence is not very important, because the two interior >< ends of -the tunnelling" canQaot in' any case be ' far. removed from each other. But in the case of the Mont Cenis tunnel-any inaccuracy in the direction ofjthe two tunnellings would hare been fatal to the success of the work, since when the two should meet it might be found that they were laterally separated by two or three hundred yards. Hence it was necessary before the work began to surrey - the intermediate country, so as to ascertain with the most perfect accuracy the bearings ■* of one end of the tunnel from the other. ' " It was necessary," says the narrative of these initial labours, "to prepare accurate plane and sections for the determination of the levels, to fix the axis of the tunnel, and to ' set it out' on the mountain top; to erect' observatories and guiding signals solid, substantial, and true." When we remember the nature of the passes over the Cenis^we can conceive the difficulty of setting out a lino of this sort over the Alpine range. The necessity of continually climbing over, rocks,— ravines, and precipices in passing from ■&--*; tionto station, involved difficulties which, ' great as they were, were as nothing when compared with the difficulties resulting from the bitter weather experienced on those rugged mountain-heights. .; The tempestt which "sweep the Alpine passes— the «verrecurring storms of rain, sleet, and driving snow, are trying to the ordinary traveller. It will be understood, therefore, how terribly they must have interfered with the delicate processes involved in surveying. It often happened that for days together no work of any sort could be done owing to the impossibility of using levels and theodolites when exposed to the stormy weather .and. Jbitter--. cold of these lofty passes. At'lengttf* how- :- eyer, thf work was completed,, and that with such success that the greatest deviation from exactitude was less than a single foot for the T whole length of seven and a half miles. ' ' '