GLACIERS OF THE CANADIAN ROCKIES AND SELKIRKS. 41 



were sawed out in various directions and melted down to thin slices by rubbing them 

 over the face of a warm saw-blade. Examining these sections with the polariscope, 

 it was found that in the case of those cut horizontally from the glacier, from 

 J to -|- of the granules remained dark when revolved. In the case of sections 

 cut vertically, either across or lengthwise of the glacier, only an occasional granule 

 was found to show this phenomenon. From this it appears that there is a ten- 

 dency towards the orientation of the granules near the lower portions of the 

 Victoria, Yoho, and Illecillewaet glaciers, a considerable percentage of the 

 granules having their main optic axes in a vertical position. The same phe- 

 nomenon was observed by Drygalski in the case of the Greenland glaciers.' 



d. Capillary structure. When glacial ice is subjected to a moderate melting 

 temperature for a sufficient length of time there is developed a network of capillary 

 tubes, at the junctions of three or more granules. These tubes are approximately 

 circular in cross-section and from 0.008 inch to 0.04 inch in diameter. Their 

 walls reflect the light strongly and give the appearance of silver threads, more or 

 less perfectly outlining the granules. From the ease with which liquids course 

 through the tubes one infers that they are free from or contain but little air. 

 From beneath the margin of the Yoho Glacier it was possible to get some of 

 them upon the camera-plate, although, many of them being out of focus, they 

 all appear disconnected (plate xii, figure i). By making a strong solution of po- 

 tassium permanganate and placing it in a basin hollowed in the ice, the capillaries 

 were in a few minutes beautifully infiltrated, the red solution contrasting strongly 

 with the rich blue ice (plate xii, figure 2). Upon the faces of crevasse walls, and 

 in the drainage tunnels, where the sides are smoothed by melting, these tubes may 

 be seen in longitudinal section, forming a pattern by which the irregular 

 granules are outlined. These are the tubes which Agassiz and Forbes found in 

 the Alpine glaciers, but which Huxley and Tyndall did not discover. Agassiz 

 was in eiTor in supposing the entire body of the glacier to be permeated with such 

 a system of capillary tubes and Huxley in denying that any part of it was. 



e. Melting features. As melting proceeds the capillaries become larger ; ir- 

 regular, "crinkly" spaces are opened between the faces of adjoining granules, and 

 the delicate network is gradually obliterated, as shown in portions of plate xii, 

 figure 2 . With this increased reflecting surface the ice loses its deep blue color, 

 becomes whiter, and when the granules are small it assumes somewhat the 

 appearance of neve. A slight pressure now, or a sharp blow, will cause the ice 

 to crumble into its component granules. These grantiles are shown, but rather 

 indistinctly, in plate xii, figure 3. While still in position, as well as after they 

 have fallen apart, the granules are seen to be covered completely with delicate 

 parallel ridges and rows of fine points winding over the surface and having no 

 definite direction with reference to the crystal. The ridges and rows of points 

 are about 0.04 inch distant, but show some variation, and form a complicated 

 pattern that is difiierent for each granule, suggesting more strongly than any- 

 thing else the ridges seen upon the inside of one's finger-tips. This phenomenon 



' Gronland-Ex-pedition der Gesellschafi fur Erdkunde zu Berlin, i8pi-gj, Bd. i, 1897, S. 494. 



