Page:Canadian Alpine Journal I, 2.djvu/106

252 tance into the ice mass. As melting proceeds these capillaries develop into narrow fissures separating the granules, and in the final stage a sharp blow will cause the ice to crumble into these component granules. It is in this granular structure that glacial ice is distinguished from that which results from the direct freezing of water, as in lakes, ponds and the pools and crevasses of the glaciers themselves. Such ice, commonly spoken of as "water-ice," consists of appromixatelyapproximately [sic] parallel prisms, arranged with their axes perpendicular to the freezing surface. This structure is often strikingly shown in the case of lake and river ice when in the spring it is undergoing disintegration.

Without attempting to draw any sharp lines of distinction between them there may be recognized four types of glaciers, all but one of which have numerous representatives in the Canadian Rockies and Selkirks. This one, not now represented, occupied the region during the previous geological epoch and its work is much in evidence in and about the mountains. These types may best be described in the order of their simplicity, frequency and development.

(a) Alpine Glaciers. In its simplest from this type originates from the snow which accumulates about a mountain pass, or within an amphitheatre, combined with that precipitated directly into the valley, or avalanched from the adjacent slopes. Having much the appearance of a great frozen river, it slowly winds its way clown the valley to a level determined by a number of factors; chief of which are the latitude, thickness of the ice, exposure to the sun, amount and distribution of rocky debris and the amount of snow and ice urging the glacier forward. Canadian examples are the Victoria, Yoho and the easternmost stream of the Asulkan