40 GLACIERS OF THE CANADIAN ROCKIES AND SELKIRKS. 



must be derived from those pellets which constitute the typical nev^. The ques- 

 tion as to how the granules are developed at once arises, btit cannot be yet an- 

 swered with certainty. (For a fuller discussion of this subject see page 127). That 

 the larger are not produced by the simple freezing together of a certain number 

 of the smaller pellets is shown b}^ the fact that each mature granule is crystallo- 

 graphicall}' homogeneous. Those who have written most recently upon the sub- 

 ject hold the view that the granules are permitted to grow by a process of partial 

 melting and refreezing, the larger thus appropriating to themselves the water 

 derived from the melting of the smaller. Miigge holds that this melting takes 

 place at the outer limits of the individual granules because of the constant read- 

 justment of pressures within the body of the glacier,^ and in this change of the 

 granules he sees the cause of glacial motion. Chamberlin believes that a similar 

 change occurs because of differential stresses upon the granules undergoing constant 

 adjustment, assisted b}' whatever heat energy may be conducted into the glacier 

 from above.2 Drygalski recently argues in favor of a melting of the granule 

 by pressure both internally and at its outer surfaces, by which some granules 

 may be completely liquified and subsequently refrozen.^ Upon this action 

 he bases his theory of glacial motion and the orientation of the granules 

 about the nose, as brought out in his Greenland report in 1897 cited below. 



Experiments of Hagenbach-Bischoff in 1 883 showed that when two ice crystals, 

 having differently directed axes, are pressed together they unite without melting 

 into a single crystal, "the larger eating t:p the smaller." The union differs from 

 the regelation of Tyndall in that there is a rean'angement of the molecules by 

 which the resultant crystal is crystallographicalh^ and optically homogeneous. To 

 distinguish it from the method of granular growth due to melting and refreezing 

 it is spoken of as a "dry union." This principle applied to the glacier would lead 

 to a continual reduction in the number of granules and a corresponding increase in 

 their size, as pointed out by Hagenbach-Bischoff, Heim, and Emden. It will be 

 shown later (page i?8) that this theory of granular growth seems to the writer 

 to best explain the remarkably perfect preservation of the often delicate laminae 

 and blue bands seen about the nose and sides of the glacier. Combined with 

 the special type of plasticity exhibited by ice crystals this method of perfect 

 dry welding may explain the absence of noticeable distortion of the ice granules, 

 which, as urged by Chamberlin, should be observed in the direction of flow if the 

 glacier moves because of its viscosity. 



In order to determine whether or not there was any tendenc}- towards the 

 orientation of the granules in the basal layers about the nose, thin slabs of ice 



'"Weitere Versuche uber die Translationsfahigkeit des Eises, nebst Bemerkungen fiber die Bedeutung 

 der Structur des gronlandischen Inlandeises," Neues Jahrbitch fur Min., Geol., und Pal., 1900, Bd. 11, 

 S. 87 zu 98. 



' "Recent Glacial Studies in Greenland," Presidential Address before the Geological Society of America, 

 Bull. Geol. Soc, vol. 6, 1895, p. 211; "A Contribution to the Theory of Glacial Motion," Decennial Publica- 

 tions of the University of Chicago, vol. ix, 1904, pp. 10 and 11; Geology, by Chamberlin and Sali.sbury 

 vol. I, 1904, pp. 299 to 306. 



3 " Ueber die Structur des gronlandischen Inlandeises und ihre Bedeutung fiir die Theorie der Gletscher- 

 bewegung," Neues Jahrbttch fur Min., Geol., und Pal., 1900, Bd. i., S. 71 zu 86. 



