Page:The New International Encyclopædia 1st ed. v. 19.djvu/623

* TUNNEL. 543 TUNNEL. miles. The tunnel on leaving Jlodane is of the followinjj dimensions: 25 feet 3% inches wide at the bottom, 20 feet 2';4 inches wide in the broad- est point, and 2-t feet 7^2 inches high, the arch being semicircular. At Bardoneechia the height is greater by 1 1 fU inches and the arch is made elliptical to enable it to resist the greater strain caused b.v a dillerent inclination of the strata. The tunnel is lined with the exception of about 300 yards on the north side. The side walls are 8 feet inches thick throughout. The arch to the south side is constructed principally of brick, and to the north side of stone, a brick key. being applied tlirou.;ihout. There are side paths of flagstones 20 inches wide. Work was begun in 1857, and for three years hanil labor was used entirely, but it was planned from the beginning by the engineers, Sommeiler, Grandis, and Grattoni, to introduce machinery ultimately. In ISGl power drills were put at work at the south end, and in 1862 the north end was similarly equipped. The drills used were o]ierated by compressed air and they and also the compressors used were invented by Sommeiler. The tunnel was completed and opened for traffic in 1872. In 1872. however, work was begun on the Saint Gotthard rail- way tunnel through the Alps between Italy and France, which far exceeded the !Mont Cenis in magnitude. This tunnel crosses the moun- tains between Goeschenen and Airolo, and is 9.25 miles long. The excavation was through rock consisting chiefly of gneiss, mica schist, serpen- tine, and hornblende, the strata having an incli- nation of from 45° to !>0°. At many points the rock was fissured and disintegrated easih', and water was encountered in large quantities, caus- ing much trouble. In this work, as at ilont Cenis, power drills and compressed air were used, but in a much improved form as a result of the pre- vious experience and years of study. The exca- vation was lined throughout with masonry', the side walls being of rubble stone and the roof arch of brick. Along the bottom there was a cul- vert of brickwork. The Jlont Cenis Tunnel had been excavated bv means of a drift as an ad- vance galler.y, but at Saint Gotthard the advance gaUer,v was a top centre heading, ^'ater power, secured by draining near-by mountain torrents, was used to compress the air used in operating the drills and for driving the compressed-air locomotives used in hauling the debris from the excavation. The tunnel was opened for traffic in 1882. The third great Alpine tunnel is the Simplon Tunnel. Hearing completion in 1904. ilany schemes for the connection of Italy and Switzer- land by a railwa.v near the Simplon Road Pass have been devised. The scheme which was put forward in 1881 by the Jura-Simplon Railway consisted broadly of piercing the Alps between Brigue, in the Rhone Valley, and Iselle. on the Italian side, from which village the railway de- scends to the southern terminus at Domo d'Os- sola, a distance of about 11 miles. Starting from Brigue. the new line, running gently up the val- ley for 114 miles, on account of the proximity of the Rhone, enters the tunnel on a curve to the right of lOoO feet radius. At a distance of 153 yards from the entrance the straight por- tion of the tunnel commences, and extends 12 miles. The line then curves to the left with a ing at the northern entrance, a gradient of 1 in 500 miles lor a length of SVa miles to a level length of 550 yards in the centre, and then a gradient 1 in 143 descends to the Italian side. The tunnel will be a double tunnel. That is, there will eventually be two parallel tunnels, having their centres 50 feet apart, each carrying one line of railway; but at the present time only one tunnel, that known as No. 1, has beett excavated to full size. No. 2 being left, masonry- lined where necessary, for future developments. Hy means of cross-headings every 220 yards, the problems of transport and ventilation are greatly facilitated. In cross-section tunnel Xo. 1 is 13 feet 7 inches wide at the bottom, and 16 feet 5 inches wide at the widest part, with a total height of 18 feet above rail-level. The n.aterial penetrated is rock. Rotary drills o]ierated by hydraulic pressure were used, there being an elaborate water-power plant at each end of the tunnel. The three great European railway tunnels which have been described find their nearest counterpart in America in the Hoosac Tunnel, the Stampede Tunnel, and the Cascade Tunnel. The Hoosfic Tunnel is on the line of the Fitchburg Railroad in JIassachusetts, and passes through a southern extension of the Green Mountains known as the Hoosac Mountains. It is 4% miles long, and was driven from the two ends and from an intermediate shaft 1028 feet deep. Work was begun originall.v in 1855 and was car- ried on intermittently, there being many long delays due to lack of funds and the obstacles en- countered. The tunnel proper was completed in 1873, but several additional years were con- sumed in the masonry work. The cost of the Hoosac Tunnel was about .$11,000,000. The tun- nel is 24 feet wide in the widest part, and 22 feet 8 inches high, and carries two lines of railway track. The Stampede Tunnel carries the Northern Pacific Railway through the Cascade Mountains, and was begun in 1886. From the time it was determined to make Puget Sound the western terminus of the Northern Pacific Railway, the question of a feasible route across the Cascade Range was prominentl,y before the company. Between the years 1873 and 1884 several proposed routes were examined by the coiupany's engineers, of which those via the Natehess, Stampede, and Snoqualmie passes were prominent. The Stampede route, l.ving beteen the other two. was finally recom- mended, and was formally adopted by the com- pan.v in 1884. Each of the routes named required a tunnel through the backbone of the Cascade Range; but the Stampede route was the longest of the three. The altitude of the mountain be- neath which it was necessary to tunnel was 3970 feet above sea-level, and the greatest thickness over the top of the tunnel is 1400 feet, the average depth being about 1200 feet. The elevation of the east portal of the tunnel above the sea is 2827 feet, and that of the west portal is 2800 feet. Work was begun in February. 1886. Probably no other tunnel was ever undertaken where the difficulties and cost of reaching the site and preparing for work were so great as at the Stampede Tunnel. The distance from the nearest railway to the east portal was S2 miles, and tn the west portal it was 87 miles, and all men, plant, and material