GLACIERS OF THE CANADIAN ROCKIES AND SEUC1RKS. 93 



Upon the face of the bedrock exposed near the nose a mark was established 

 September 16, 1903, immediately beneath the nearly vertical side of the ice, 

 the height of which was estimated as 60 feet. August 24, 1905, it was found 

 that the ice had withdrawn laterally 2.4 feet from the face. Passing around from 

 the nose eastward, three stations were established along the margin of the ice. 

 A large boulder was found just emerging from the ice, the first week in September, 

 1904, and marked "Face emerging, Sep., "04." Upon the 24th of August, 1905, 

 it was found that the ice had retreated here 14 feet. Farther along a medium- 

 sized boulder had been marked in 1903, "15 ft. to ice. ix-i6-c>3." By Sep- 

 tember i, 1904, a retreat of 12.5 feet had occurred here, while at the upper 

 station the boulder "27 ft. to ice. ix-i6-c>3," measured September 3, 1904, 27 

 feet, and August 25, 1905, 27.1 feet. These data indicate that the margins of 

 the ice have been receding as we approach the nose, more rapidly upon the eastern 

 side, but that farther up along the margin there has been no change for the last 

 two years and, very probably, for a considerably longer time The two views on 

 plate xxxvi, taken from almost identically the same view-point, the former in 

 1888 and the latter in 1905, furnish a good opportunity for noting the changes 

 produced in the glacier in the 17 years. It seems almost possible to recognize 

 the individual trees standing to the right of the center, but the lower half of the 

 glacier is unrecognizable. A stadia and trignometric survey of the Illecillewaet 

 and Asulkan glacier tongues was made in 1906 by the Messrs. Vaux and a 

 report made to the Philadelphia Academy of Sciences. Some additional data 

 concerning the movements of the steel plates upon the Illecillewaet were collected 

 and appear upon plate xxx of this report. 



b. Ice waves. In comparing their photographs made in 1898 and 1899 from 

 a certain large boulder, just west of the trail, Messrs. Vaux noted an apparent 

 thickening in the ice just beneath the neVe" line. By drawing a delicate line be- 

 tween corresponding points in figures i and 2, plate xxxvi, that may be recog- 

 nized in the upper ne"vd region, it is seen that the ice margin along the sky-line 

 stands slightly higher in the 1905 view. The difference is slight, however, and can 

 represent but a few feet. When the Notman view of 1888 is compared with a 

 second, which was made in 1897, and here reproduced in plate xxxvn, figure 2, 

 the heaping of the ice line beneath the neVe" line is still more plainly seen. There 

 is thus evidence that a wave, or impulse, derived from an increased precipitation 

 over the ne"ve" region, travels the length of the glacier and gives rise to a halt, 

 or an advance, of the front; followed by a depression which permits of a retreat. 

 Such a depression appears to have been at the edge of the ne"ve" line in 1887 or 8, 

 while the glacier about the lower extremity was experiencing the effect of a pre- 

 vious impulse. The retreat of the glacier was greatest between 1890 and 1900, 

 and if we assume that it culminated at about the middle of the decade, it required 

 about 8 or 9 years for this trough of the wave to reach the nose, or at the average 

 rate of 800 to 850 feet per annum. Since in 1905 the appearance of the sky-line 

 along the ne"ve" corresponds so nearly with that seen in 1888, we may assume that 

 the crest of the wave was in this position at a date only a little later than the 



