GLACIERS OF THE CANADIAN ROCKIES AND SELKIRKS. , 45 



Wherever observed, the phenomenon of blue bands suggested the structure 

 in rocks known as schistosity, rather than stratification, the bands thinning out 

 and overlapping. It is possible that they may still be due to pressure and yet 

 the ice may not have become liquid, as Tyndall supposed in order to account 

 for the scarcity of air bubbles in the blue bands, when compared with the whitish 

 vesicular ice in which they are embedded. There may be serious doubts as to 

 whether the pressure has been sufficient to produce liquefaction in all such cases 

 where the bands occur, and there is no reason for thinking that the crystalline 

 condition of the ice would be essentially different in refreezing. We may account 

 for the irregular and often contorted banding (plate xm, figure 2) by assuming 

 that differential movements have occurred in the ice mass since the bands were 

 formed. A double set might be induced without the complete obliteration of the 

 first. It is quite possible that, in the case of a glacier of the simplest supposable 

 type, having a very even bed and without the restraint of rocky walls or lateral 

 moraines, the original lamination of the neVe" would be preserved to the nose 

 and give rise to a certain type of "blue band." It would seem that such a type, 

 however, could be distinguished from the more common variety and that it 

 would lose in distinctness towards the nose. The writer had come to the con- 

 clusion that the diverse views held by investigators concerning the origin of 

 these bands were due to the fact that two very similar structures had been 

 studied under the same name, when his attention was attracted to the following 

 paragraphs written by Agassiz when glacial study was still in its infancy : 



"Undoubtedly, in both these instances, we have two kinds of blue bands, 

 namely: those formed primitively in a horizontal position, indicating seams of 

 stratification, and those which have arisen subsequently in connection with the 

 movement of the whole mass. . . . With these facts before us, it seems to 

 me plain that the primitive blue bands arise with the stratification of the snow 

 in the very first formation of the glacier, while the secondary blue bands are 

 formed subsequently, in consequence of the onward progress of the glacier and 

 the pressure to which it is subjected. The secondary blue bands intersect the 

 planes of stratification at every possible angle, and may therefore seem identical 

 with the stratification in some places, while in others they cut it at right angles." 

 Geological Sketches, vol. i, pp. 260 and 261. 



In this report the writer uses the term lamina by which to refer to these 

 ' ' primitive blue bands ' ' arising in the neVe, and blue bands for the similar, but 

 essentially different, structure resulting, apparently, from pressure, or from some 

 other possible agency. 



g. Ice dykes. These were well developed upon the lower Lefroy in the early 

 part of the summer, but became somewhat obscured as the season advanced. 

 They were found sparingly upon the Wenkchemna, but were not observed upon 

 the other glaciers studied. They consisted of gashes in the body of the ice, 

 apparently former crevasses, from two to fifteen inches across, which were filled 

 with columnar ice crystals. The columns varied in diameter from J to i inch 

 and stood at right angles to the crevasse walls, having thus an approximately 



