The Spiral Tunnels

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THE SPIRAL TUNNELS RIOR to 1908 Hector and PRIOR Field stations were sepa- rated by such extreme grades that four consolidation loco- motives were required to haul a trainload of freight over this section. For about three miles a grade of 4.5 per cent prevail- ed ten times the maximum gradient normally permitted on heavy prairie work. By the construction of these Spiral Tunnels this grade was reduced to 2.2 per cent. From the east, the track enters Tunnel No. 1, 3,206 feet in length, turns under Cathedral Mountain at an angle of about 250 degrees on a 573 foot radius, passes under itself and emerges at the opposite portal 54 feet lower. Tunnel No. 2, under Mount Ogden, has a similar radius through an angle of 232 degrees; it is 2,890 feet long and the grade produces a difference in elevation of about 45 feet between portals. Thus the railway traverses the valley by three lines at different elevations, and crosses and re-crosses the Kicking Horse River by four bridges. Two engines can now haul a bigger load up the valley than the four previously used. The two tunnels are a per- fect maze, for the railway doubles upon itself twice and forms a rough figure "8" in shape. If the train is run in two sections, passengers are able to see the other section making its way up "the big grade" at a higher or lower level. WHITE DOTTED LINES REPRESENT THE ROUTE FOLLOWED BY CANADIAN PACIFIC TRAINS THROUGH THE FAMOUS SPIRAL TUNNELS.

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