EXTINCT AND EXISTING GLACIERS OF COLORADO 4 1 



ing analogous to cleavage, which is occasioned by pressure of the mov- 

 ing ice, being especially developed in constricted or very steep parts of 

 the glacier." Two years later he announced' that he had followed the 

 outcrops of strata from the neve practically to the end of the glacier and 

 convinced himself that "banded structure is the modified appearance 

 of the outcrops of original stratification." He, however, distinguishes 

 the stratification, and blue bands from the banded structure due to 

 pinched crevasses (i.e., crevasses which have closed, but still show on 

 the surface). 



The strongest argument which can be used to show that the blue veins are 

 merely the transformed strata is that in some glaciers the stratification can be 

 followed step by step from the reservoir to the lower part of the glacier, where 

 it is seen to correspond to the blue veins. The Unteraar and the Forno glaciers 

 are the only two large glaciers where this has actually been done, but on these 

 glaciers the observation is decisive. On many small glaciers the strata can be 

 followed to the end, but in these cases it rarely happens that they have been 

 completely transformed into blue bands. ^ 



Sherzer'' concluded that "in the case of the Canadian glaciers 

 studied it seems probable that the strata are depositional, in very 

 large part, at least. The stratification of the Victoria continues 

 throughout the glacier's extent." He leaves the matter of the blue 

 bands in doubt, but inclines to Tyndall's pressure theory (pp. 77, 87, 

 122). In any event, if the blue bands represent original stratification, 

 much modification has occurred. 



Dirt-Bands, Zones and Stripes. — Dirt-bands and stratification 

 are intimately associated. Different kinds of bands from different 

 causes have been confused under one term. They have recently been 

 ably discussed by Sherzer.'' The lines of demarkation between strata 

 are usually soiled streaks. Any rest from deposition sufficient to 

 allow the fresh surface to solidify somewhat from the action of the 



» Reid, Harry Fielding, "Stratification and Banded Structure of Glaciers" (abstract), Science, N.S., 

 Vol. XI, pp. 103-4, 1900. 



' Reid, Harry Fielding, "The Flow of Glaciers and Their Stratification," Appalachia, Vol. XI, p. 6, 

 igos. 



3 Sherzer, William Hittell, "Glaciers of the Canadian Rockies and Selkirks," Smithsonian Contrib. 

 to KnowL, Pub. No. 1692, Vol. XXXIV, pp. 22, 38, 42-45, 122, 1907. 



< Sherzer, William Hittell, " Glacial studies in the Canadian Rockies and Selkirks," Smithsonian 

 Miscell. Coll., Pub. No. 1567, Vol. XL VII, pp. 465-69, 1905; "Glaciers of the Canadian Rockies and Sel- 

 kirks," Smithsonian Contrib. to KnowL, Pub. No. 1692, Vol. XXXIV, pp. 39, 50-54. "8, 119. 



