46 GLACIERS OF THE CANADIAN ROCKIES AND SELKIRKS. 



horizontal position. Very commonh' the inner ends of the columns met and 

 interlocked at the centre, but sometimes they were simply attached by their 

 bases to the crevasse walls and left a space at the centre. Plate xiii, figure 3, 

 will give some idea of the appearance of these dykes, although the individual 

 ice crystals could not be made to show in a general view. As a rule the columns 

 were straight, but sometimes curved and geniculated. The dykes were some- 

 times many feet in length, occasionally cutting across the walls of crevasses, 

 presumably younger in age. In certain cases similar columns were found filling 

 elliptical cavities in the ice, the crystals meeting at the centre. Such structures 

 as these were observed by Agassiz upon the Aar Glacier and described by him 

 in 1847 under the name of "glace d'eau." ^ Although their origin was not under- 

 stood he clearly saw that they resulted from the freezing of water in cavities in the 

 ice. The ellipsoidal cavities with their radially aiTanged columns were figured 

 upon plate vi of his atlas and described under the name ' ' ctoile de glacier, ' ' 

 or " Gletscherstern" (p. 187). These structures probably arise from the freezing 

 of water-filled crevasses, moulins, and smaller cavities, the cooling surfaces being 

 the walls of the cavity, instead of the atmosphere. When a lake surface freezes 

 similar columns of ice are formed, with their main axes at right angles to the 

 cooling surface, and, hence, ordinarily vertical. In the case of these d}'kes the 

 columns also take a position at right angles to the surface of refrigeration, 

 but these surfaces now being vertical the columns assume a horizontal position.^ 

 If the freezing is complete, the columns meet at the centre, the growth of the 

 columns proceeding at about the same rate, inward from the sides. Shotild the 

 water be drained off before the freezing is complete a space will be left at 

 the centre. They are probably formed in the early part of the season, while the 

 body of the glacier still retains some of its winter's temperature and after the 

 melting has proceeded far enough to supply the necessary Avater. After being 

 once fomied they would persist through many seasons, although their upper 

 surfaces might be obscured by various agencies. Somewhat similar dykes were 

 sparingly observed upon the western side of the Lefroy but filled with granular 

 ice, instead of the ice columns. Obviously these have had an entirely different 

 history. The most plausible explanation is that they represent crevasses 

 which were filled with the granular ice avalanched from the hanging glacier 

 upon Mt. Lefroy. 



2. Surface Features. 



a. Superficial debris. The narrow valley through which flows the upper 

 third of the Victoria Glacier, permits the avalanches of snow and ice to distribute 

 rock debris over the entire surface. The most of this material is derived from 

 the Mt. Victoria side, from which the avalanches may shoot completely across 



• Nouvelles Etudes et Experiences sur les Glaciers Actuels, 1847, Premiere Partie, p. 185, plate vi, 

 figures 14, 15, et 16. 



2 While this report is going through the press the author has been enabled to study the valuable paper 

 of Crammer referred to upon page 43. Under the head of Leisten he describes similar structures (p. 104) 

 and ascribes to them the origin here given. 



