THE SNOW-SHEDS OF THE SELKIRKS.
Owing to the heavy precipitation and consequent enormous accumulation of snow during the long winter, on the mountains of the Selkirks, the avalanche is a distinct danger to the railway in the narrower valleys and passes. In the spring the snow may weigh almost 50 lbs. per cubic foot, and very little will start an avalanche. Its powers of destruction are terrible. Therefore, wherever there is exposure, the track is protected by snow-sheds. Albeit built for stern utility without regard to beauty, their achitecture is of interest. Indeed, looking through the long vista of an interior, the lines of its rafters are not unbeautiful.
There are five types of snowsheds. (1) If the surface is at a steep angle the uphill side is held by a retaining crib of cedar logs. The rafters are supported by one end of this crib, and the other end is carried by a framed bent, the middle of the rafter being supported by struts. As a rule, the bents are five feet apart between centres, but at places where unusually severe avalanches may be expected, the distance is reduced to four. Shed rafters are usually of Douglas fir and are 12 by 15 inches in size, the plumb and batter posts being 12 by 12. The bents are supported either by piles or mud sills.
The second type is made to suit a flatter slope. The crib is only carried up half way, and a framework of posts and rafters is built on top. In the third type the crib is omitted altogether. In the fourth, known as the "valley-type" and built to resist avalanches from either side, the cribs are built on both sides and the rafters laid directly across. The fifth type is used for those places where the track is cut out of the hill-side and where the avalanche must fall nearly vertically on the snowshed. Its rafters are trussed and the sheds more strongly built.
As snowsheds are subject to fire, ample fire protection is provided. There is a complete system of piping throughout, and the shed itself is broken into short lengths separated by fire-breaks. These breaks are covered by split fences made of heavy V-shaped cribs to guide the slide over the adjacent sheds. There is also a thorough system of patrol and should fire break out a watchman would be on the spot speedily.
There are altogether six miles of snowsheds from six miles east of Rogers Pass to fifteen miles west of Revelstoke in the Gold Range. The average cost of building is some $40 a foot.
