Page:Whymper - Scrambles amongst the Alps.djvu/87

Rh estimate," says M. Conte, "that the sinking of a shaft a mile in depth would occupy not less than forty years. I do not know that a depth of 1000 feet has been hitherto passed."

"Several projects were presented to the Sardinian government, some proposing to shorten the length of the tunnel by raising its level, and others to accelerate the boring of the holes for blasting; but they were all put aside as impossible, or as having been insufficiently studied. The first one seriously considered by the government was that of M. Maus, a Belgian engineer. He proposed to construct a tunnel of 12,230 mètres between Bardonnêche and Modane, with a ruling gradient of 19 in 1000. The advance of the small gallery in front was to be made by means of a machine with chisels, put in motion by springs, that would have cut the rock into blocks—leaving them attached only at the back—which were afterwards to be brought down by means of wedges."

"M. Colladon of Geneva suggested moving the tools of the machine of M. Maus by means of compressed air, but he neither pointed out the means of compressing the air, nor how it was to be applied as a motive power."

"The government had constructed the railway from Turin to Genoa, and engineers were studying how to tug the trains up the incline at Busalla, which has a gradient of 1 in 29. MM. Grandis, Grattoni, and Sommeiller proposed to compress air by means of the 'compresseur à choc' which is now used on the works of the Cenis tunnel, and to employ it for the traction of the trains."

"Mr. Bartlett, an English engineer on the Victor Emmanuel Railway, had invented a machine for making holes for blasting,