The considerations which decided the Italian engineers upon selecting this position for the contemplated tunnel, were principally the following: first, it was the shortest route that could be found; secondly, the difference of level between the two extremities was not too great; and, thirdly, the construction of the connecting lines of railway--on the North, from St. Michel to Fourneaux, and on the South, from Susa to Bardonnêche were, as mountain railways go, practicable, if not easy. The idea of a tunnel through the Alps had long occupied the minds of engineers and of statesmen both in France and Italy; but it is to the latter country that we must give the credit of having worked the idea into a practical shape, and of having inaugurated one of the most stupendous works ever undertaken by any people. To pierce a tunnel seven and a half English miles long, by ordinary means, through a hard rock, in a position where vertical shafts were impossible, would be an exceedingly difficult, if not, _in a practical point of view, an impossible_ undertaking, not only on account of the difficulties of ventilation, but also on account of the immense _time_ and consequent expense which it would entail. It was evident, {61} then, that if the project of a tunnel through the Alps was ever to be realized, some extraordinary and completely new system of mining must be adopted, by means of which not only a rapid and perfect system of ventilation could be insured, enabling the miners to resume, without danger, their labors immediately after an explosion, but which would treble, or at least double, the amount of work usually performed in any given time by the system hitherto adopted in tunnelling through hard rock. To three Piedmontese engineers, Messrs. Grandis, Grattoni, and Sommeiller, is due the merit of having solved this most difficult problem; for whether the opening of the Alpine tunnel take place in ten or twenty years, its ultimate success is now completely assured. A short review of the history of this undertaking, and a summary of the progress made, together with a description of the works as they are conducted at the present time, derived from personal observation, cannot fail to be interesting to English readers.