there is more or less of a horizontal component. The chief factors concerned are the configuration of the collecting area and the weight of the accumulated snow. If movement is not permitted the entire mass remains a snow bank, or heap of stagnant ice which does not possess the essential characteristics of a glacier.
Space does not permit the discussion here of the distribution of modern and ancient glaciers over the face of the earth by which the application of the above conditions might be more readily comprehended by the reader. In general it may be said that when a glacier exists today these four conditions have been satisfactorily met in the past, although one or more of them may be now lacking. If a given area does not support a glacier, one or more of these conditions has been wanting, just which ones being readily determined by an inspection of the region. In the Canadian Rockies and Selkirks we find ideal conditions for glacier formation: broad valleys, basins and gentle slopes; high altitude and latidude; moisture-laden winds from the Pacific, causing heavy snowfall upon the western slopes and about the crests of these great systems.
When exposed to the warm rays of the sun the snowflakes melt into small globules which are subsequently frozen into pellets resembling granular tapioca. The snow in this condition is flnown as firn or névé, and from its consolidation the glaciers take their origin. In some way not yet fully understood the granules of the névé gradually diminish in number and increase in size until they attain the size of hazel-nuts or walnuts, or even the size of the fist in large glaciers like the Yoho and Illecillewaet. So long as the temperature of the ice is well beneath the freezing point these granules are not in evidence, the ice appearing compact and homogeneous. When, however, it begins to feel the effect of a higher temperature, there appears a delicate system of capillary tubes, outlining the granules and extending some dis-
