In the middle of the tunnel line beneath the rails, there is made at the same time with the excavation, a covered way or drain, in which are laid the pipes for gas, water, and compressed air. By this drain the waste water runs off, and it is also intended to serve as a means of escape for the workmen, in case of a fall of rock, or other accident which might block up the tunnel. Of course the tunnel must be continually supplied with fresh air along its whole length, as well as at the heading. This is easily done from the compressed air tube in the covered drain. The whole length of the Mt. Cenis tunnel is through rock varying in hardness, and veined throughout with quartz. In many parts it is liable to flake off, and in some places considerable masses have broken away during the construction. The full section of the tunnel is twenty-six feet and three inches wide, and twenty feet and eight inches high. The heading is carried forward about eleven and a half feet wide and nearly ten feet high. At the time of Mr. Storrow's visit the drilling machines were used only in the heading. The whole of the enlargement was done by hand labor in the ordinary way. The drills when brought up to the work drill eighty holes before any blasting is done. About ninety workmen are employed at each end. It required from five to seven hours to drill the eighty holes. Mr. Storrow visited a workshop where some machines were ready, and a large block of stone was placed in front of them for trial. The air was let on and a drill put in motion. In 6 1-2 minutes it drilled 5 1-2 inches. The engineer stated that they would make better progress than that at the rock in the tunnel. The average progress made by hand was about sixty-six feet a month. That rate was about doubled by means of the machines; but since Mr. Storrow's visit these machines have been greatly improved, and the rate of progress latterly has been about two hundred feet a month. The opening of the Mt. Cenis Tunnel was commenced in October, 1857. Up to July, 1861, about 2142 feet had been excavated, the average progress being about sixty-six feet a month. The machines were then introduced, and at the present time, upwards of three miles have been excavated, and at the rate of progress now being made the tunnel will be completed in four years. Mr. Storrow's estimate of its cost is $640 per running yard.