122 GLACIERS OF THE CANADIAN ROCKIES AND SELKIRKS. 



position. The average daily melting about the spikes in the upper stratum was 

 0.23 of an inch in excess of that about those in the lower and proved that a differ- 

 ential movement of the strata was taking place. 



c. Blue bands. It seems highly desirable to distinguish the minor stratifica- 

 tion seams, originating in the ne"ve", from the blue bands, blue veins, or ribbon 

 structures, that have had an entirely different origin. The first step toward 

 such distinction is to have a separate term for each of the two types of structure 

 and the writer suggests that lamina be used exclusively for the minor layers of 

 which the strata are composed and that blue bands, 1 already in such general use, 

 be restricted to the structures commonly included under the term, however 

 they may have been produced. When they are each made the object of com- 

 parative study it should be possible to distinguish them. We should naturally 

 expect the laminse to become less and less distinct toward the nose, and to appear 

 continuous, while we find the blue bands there showing very typically and being 

 discontinuous. The same stratum might show both structures, either conform- 

 able, or cutting one another at various angles. In the case of simple glaciers, 

 Agassiz and Reid have succeeded in tracing the laminae from the neVe" to the nose. 

 The structures seen in the Canadian glaciers are blue bands, rather than 

 laminas, since they are developed in great perfection where the strata have been 

 completely destroyed, as in the case of the regenerated Lefroy and almost 

 obliterated as in the Yoho and Illecillewaet glaciers. In general their position is 

 at right angles to what may be assumed to be, or to have been, the direction of 

 maximum pressure. They are seen best along the margins where the glacier is 

 closely confined between rocky walls, extending parallel with the sides, dipping 

 downward and inward at a steep angle. Beneath the medial moraine upon the 

 Victoria they are vertical to fan-shaped. At the foot of ice cascades they may 

 extend crosswise of the glacier. Having the same origin and being essentially 

 alike, it does not seem wise to use different terms by which to separate these, 

 such as marginal structure, longitudinal structure, and transverse structure, as 

 suggested by Tyndall. Contorted patterns and faultings are to be accounted for 

 by assuming differential movements in the ice after the formation of the bands. 



When followed for a short distance, in either direction, blue bands are found 

 to thin out to an edge and disappear, showing that they have a very flat, 

 lenticular shape. Separate bands overlap and are felted together as are the 

 bands in a schistose or gneissic rock. They strongly suggest schistosity in rocks 

 and not stratification. The ice of which each band is composed is more compact, 

 more free from air bubbles, and a deeper blue than the ice in which it is embedded. 

 That they have been produced by pressure and stand at right angles to it, when in 

 process of formation, as demonstrated by Tyndall, seems most probable. That 



1 The term band alone, or banding, as suggested by the glacial conference in August, 1899, is not fully 

 satisfactory since it does not distinguish this structure from the dirt bands of Forbes. The following terms 

 have been applied to this structure by various writers; Bandstruktur, Banderung, Blaubanderung, Blatter- 

 struktur, Blaublatterung, Blaublatterstruktur, blaue Bander, blaue Streifen, Schieferung, Schichtung, 

 parallele Struktur, stucture rubanee, structure lamellaire, ribboned structure, blue veins, blue leaves, blue 

 bands, lamellae, laminae, lamination, and stratification. 



