GLACIERS OF THE CANADIAN ROCKIES AND SELKIRKS. 43 



become indistinct in proportion as the granules separate. In the moulins, 

 opposite the obHque ice face the average inchnation up-stream was found to be 

 30°. Under the medial moraine, near the nose of Mt. Lefrov, the bands were 

 longitudinal, vertical near the centre but radiating, fan-like, upon either side; 

 the outer ones inclining as much as 45°. Although for over 65 years the subject 

 of study, we are not much nearer an explanation of this common glacial feature 

 than when first observed in 18 14 by Brewster. The idea of Forbes that they 

 represent ice-filled crevasses, or shearing-planes, has been generally abandoned. 

 The early view of Agassiz, that they represent the original lamination of the nev6 

 snow, successively compacted by rain or melting, and then frozen {Geological 

 Sketches, p. 247), has been revived by Reid ' and Hess.^ Crammer accepts 

 this same view of the origin of these bands, and argues further that they repre- 

 sent shearing-planes along which the motion of the glacier proceeds.^ In his prize 

 essay, tjber das Gletscherkorn, p. 37, Emden advances the theory that these blue 

 bands were formed by the overflow from glacial brooks, infiltrated and frozen. 

 The view of Tyndall, that these blue bands result from pressure and, when 

 formed, are at right angles to it, had received very general acceptance. In 

 the former view the lamination is to be regarded as an organic part of the glacier; 

 in the latter, the banding is of secondary origin, and might not be present at all, 

 under certain circumstances. Tyndall 's theory is set forth clearly in his Glaciers 

 of the Alps, chapter 31, and is summarized thus: ''The ice of the glacier must 

 undoubtedly be liquified to some extent by the tremendous pressure to which it 

 is here subjected. Surfaces of discontinuity will in all probability be formed, 

 which facilitate the escape of the imprisoned air. The small quantity of water 

 produced will be partly imbibed by the adjacent porous ice, and will be refrozen 

 when relieved from the pressure. This action, associated with that ascribed to 

 pressure in the last section, appears to me to furnish a complete physical expla- 

 nation of the laminated structure of glacier-ice." 



The Lefroy Glacier, being a regenerated and at the same time a parasitic one, 

 moving in a different direction from its host, furnishes an opportunity for testing 

 our two theories. In plunging 2,000 feet into the valley all traces of the original 

 stratification and lamination of the neve must be destroyed. Since the avalanches 

 of snow and ice occur only, or mainh', during a few months of the year, it may 

 be safely granted that la^'ers of this material will be spread out, more or less 

 unevenly, about the base of the cliff, alternating probably with layers of snow 

 which falls directly into the valley, or is in part drifted there. The result of this 

 action will be to restore the stratification seen in the hanging glacier at the crest 

 of the precipice. It cannot be assumed, however, that anything like the 

 original lamination of the ice can be reproduced. Possibly around the margin 

 of the area covered by the avalanches, there might be built up a succession of 



' " The Relation of the Blue Veins of Glaciers to the Stratification," Comptes Rendiis IX. Congres Geol. 

 Interimt. de Vieitne, 1903, pp. 703 to 706. 



' Die Gletscher, 1904, p. 175. 



' Eis- iind Gletschersttidien. Neues Jahrbuch fur Min., Geol., und Pal., xviii. Beilage-Band, 1904. 

 pp. 105 and 106. 



