Engineering Wonders of the World
Volume III

154 ENGINEERING WONDERS OF THE WORLD. has a piston area of 15| square inches ; and as the water pressure is about 1,500 lbs. to the square inch, the total ram thrust is over ten tons. To sink a hole 39 inches deep takes from twelve to fifteen minutes. Engineers who have used it maintain that the Brandt THEODOLITE STATION ON MONT LEONE, 7,000 FEET ABOVE THE LINE OF THE SIMPLON TUNNEL. {Photo, by courtesy of Mr. Francis Fox.) drill has done more than anything else for the progress of rock tunnelling. The ventilation in the workings of the Arl- berg Tunnel was good—far better than in those of the St. Gothard and Mont Cenis. Large Ventilation. pipes were brought up to the working faces, and from them was squirted water in fine jets after a blast explosion to lay the dust and absorb the fumes of the explosive. Also, fresh air was pumped by electrically driven pumps through other pipes and delivered where needed. Steam locomotives were used for haulage, but so constructed that the fires could be banked down and the smoke confined while an engine was inside the tunnel. From the Arlberg we pass to the longest, and in many ways the most interesting, tun- nel yet constructed—the great The Simplon |2|-mile bore under the Sim- Pass. pion Pass. Since the time of the Romans, and probably since a date much earlier than that of the founding of Rome, the Simplon Pass has been one of the chief routes over the Alps. The present excellent but little used roadway was completed, by order of Napoleon, in 1805. It is 37| miles long, and cost over £300,000 to construct. During the latter half of last century many schemes were mooted for taking a railway through the pass. Of these, all but two in- cluded a summit tunnel. In 1879 the JurarSimplon Railway Pro^ects 1°r was brought from the east end of the Lake of Geneva up the Rhone Valley to Brieg, at the north end of the pass, where it had to stop ; and at about the same time the Italians had pushed a track up to Lake Maggiore. In 1881 the Jura-Simplon Com- pany proposed piercing the mountains between Brieg and Iselle, in the narrow valley of the Diveria on the Italian side. A tunnel at this point would bring north-western France nearer SIGNAL STATION ON MONT LEONE, CAPPED WITH Ä A CONE OF ZINC. Many of these stations were built to assist the trigono- metrical survey made to establish the centre line of the Simplon Tunnel. {Photo, by courtesy of Mr. Francis Fox.) to Italy, cutting off between Calais and Milan no less than 80 and 95 miles as compared with the St. Gothard and Mont Cenis routes re- spectively. To secure fast and cheap traffic the tunnel must be at low level, to permit easy grades on the approaches, and therefore be of great length.