Engineering Wonders of the World
Volume III

158 ENGINEERING WONDERS OF THE WORLD. length of but 40 metres, six months were consumed in driving the heading, and another year in getting in the lining. The cost came out at £1,000 for every yard run. This, however, is not surpris- ing, in view of the fact that the tun- REMOVING FALSE ARCHES, SIMPLON TUNNEL. badly fis- sured, and discharged a quantity of hot water at such pressure as to detach and fling pieces of rock large enough to inflict seri- ous injury on the miners. The heat of the workings became al- most unbear- able, although the rocks were Hot Springs struck on the Swiss Side— nel had to be enlarged laboriously by hand to full section, and the space outside th© frames . . then filled with temporary Costly Work. . masonry, to give support ioi the timbering of the space subsequently- excavated for the permanent lining, which was five feet thick. This stage of the work, besides causing much serious delay, taxed the men severely. The stream of water mingling with the decomposed schist formed a slush in which the men were often sunk waist deep. To their credit be it said that such discomfort did not slacken their deter- mination to overcome the immense difficulties with which they had to contend. Meanwhile, in the Swiss portion of the tunnel excellent progress had been made, and the centre point was reached several months ahead of time. In order to take full advantage of this, the headings were continued on a slightly rising gradient to the roof-level of the tunnel a short way down the Italian decline. Then the headings were given a downward slope of 1 in 40. Unfortunately, the rocks at this point were deluged with cold water piped up the tunnel. Eventually a point was reached at which, owing to th© depth of water accumulated, it became necessary to turn the headings up- wards once more, on the very gentle gradient of 1 in 1,000. As a precaution iron doors were placed in both headings at the point Summit Level ------of Tunnel SWISS 1 in 666 ... If 'W Iron SWISS Door t in io«« ■WJJWWIWT SKETCH SHOWING HOW HEADINGS WERE DRIVEN AT THE POINT OF MEETING IN THE MIDDLE OT? THE SIMPLON TUNNEL. The Italian party tapped the water accumulated in the southernmost Swiss heading on 24th February 1905, six and a half years after boring commenced at the entrances. where the up-grade began, to be closed in case of an emergency. This proved to be a very wise step, for shortly afterwards an un- usually hot spring was tapped, and, the cold water supply breaking down, the miners had to retire, making the doors fast behind them. The situation now looked very serious in-