MOUNT CENIS TUNNEL

first great Alpine tunnel to be completed. It lies under the Frjus Pass, from Modane, France, to Bardoncchia, Italy. The 8.5-mile (13.7-kilometre) rail tunnel, driven from two headings from 1857 to 1871, was constructed under the direction of Germain Sommeiller, and it pioneered several techniques, notably the use of dynamite in rock blasting, an improved rock drill invented by Sommeiller, and compressed-air machinery developed by Daniel Colladon of Geneva. Mount Cenis was the first long-distance rock tunnel driven from two headings with no intervening shafts and as such remains a landmark engineering achievement. Running roughly parallel with it is the Frjus Tunnel (8 miles long), which was completed in 1980 and carries automobile traffic.