use on the Big Hill. Baldwin Locomotive Works was called upon to build two 2-8-0s for use as Field Hill pusher engines in 1884. At the time they were the most powerful locomotives built. Two more followed in June 1886. The CPR began building its own 2-8-0s in August 1887, and over the years hundreds more were built or bought. Spiral Tunnels The Big Hill "temporary" line remained the main line for 25 years until the spiral tunnels were opened on September 1, 1909. The improvement project was started in 1906, under the supervision of John Edward Schwitzer, the senior engineer of CPR's western lines. The first proposal had been to extend the length of the climb, and thus reduce the gradient, by bypassing the town of Field at a higher level, on the south side of the Kicking Horse river valley. This idea had quickly been abandoned because of the severe risk of avalanches and landslips on the valley side. Also under consideration was the extension of the route in a horseshoe loop northwards, using both sides of the valley of the Yoho River to increase the distance, but again the valley sides were found to be prone to avalanches. It was the experience of severe disruption and delay caused by avalanches on other parts of the line (such as at the Rogers Pass station, which was destroyed by an avalanche in 1899) that persuaded Schwitzer that digging spiral tunnels was the only practical but expensive way forward. The route decided upon called for two tunnels driven in three-quarter circles into the valley walls. The higher tunnel, "number one", is about in length and runs under Cathedral Mountain, to the south of the original track. When the new line emerges from this tunnel it has doubled back, running beneath itself and lower. It then descends the valley side in almost the opposite direction to its previous course before crossing the Kicking Horse River and entering Mount Ogden to the north. This lower tunnel, "number two", is a few yards shorter than "number one" and the descent is again about 50 feet. From the exit of this tunnel the line continues down the valley in the original direction, towards Field. The constructions and extra track effectively double the length of the climb and reduce the ruling gradient to 2.2%. The new distance between Field and Wapta Lake, where the track