As tunnel-boring operations upon such a scale as this were in their infancy, this engineer-in-chief perforcedly had to break a great deal of new ground; to carry out considerable pioneer work. Hitherto, the usual tools at the service of the excavators were the pick-axe, shovel, chisel, and sledge-hammer; but such implements as these in a work of this magnitude were akin to forging a mighty crank shaft with a blacksmith’s hammer. New forces had to be created. The Mont Cenis had demonstrated this fact, and in the course of its realisation a new tool appeared. This was the mechanical percussion rock drill, operated by compressed air at a pressure of 112 pounds and upwards per square inch. To furnish the requisite energy to the tools elaborate air-compressing plants had to be laid down. These were designed by Professor Colladon, and they were capable of compressing 1,596 cubic yards of air to a pressure of eight atmospheres every minute, the power being stored in huge cylindrical reservoirs, not unlike mammoth steam boilers, from which the conduits extending to the working faces on either side were charged. The scene in the tunnel was impressive in the extreme. At the working face a little gallery was bored, about eight feet wide by the same in height, at the roof of the tunnel. The drilling machines were mounted on travelling carriages, with their perforating chisels jutting ugly and business-like from the front. With the pent-up force of eight atmospheres behind them, they rapped against the solid rock and slowly but surely made a perforation. At frequent intervals there was a slight stop, the chisel point was withdrawn and a jet of water, drawn from a tender hauled up in the rear, was directed into the hole, when the chisel instantly resumed its monotonous round. At intervals, a chisel, with its cutting edge blunted from continual hammering at the iron-like mass, was taken out, thrown on one side, and another inserted in its place, to continue the attack on the rock. Progress was laboriously slow, or comparatively rapid, according to the nature of the material encountered. When the rock was of a granitic nature, then advance was only at the rate of an inch or two per hour; on the other hand, when soft, clayey material was tapped, then the chisels bored their way at the rate of as many feet in the same time. [Illustration: THE COMPRESSED AIR LOCOMOTIVE WHICH HAULED WORKMEN AND ROCK BLASTED FROM THE MOUNTAIN IN THE CUTTING OF THE LOETSCHBERG TUNNEL] [Illustration: WHAT THE WORKING FACE IN THE HEART OF THE MOUNTAIN IS LIKE The gang and drills cutting the path for the line through the Loetschberg Tunnel recently completed. BORING A GREAT ALPINE TUNNEL] [Illustration: _Photo by E. Goetz, Lucerne_] THE LOFTY AMSTEG BRIDGE, 184 FEET HIGH, SPANNING THE MADERAN VALLEY ON THE ST. GOTTHARD RAILWAY]