GLACIERS OP THE CANADIAN ROCKIES AND SELKIRKS. 9I 



the mean summer motion of the two most easterly plates was less than their 

 yearly average. It is to be noted that the maximum summer movement of 6.96 

 inches (July 31 to August 11), 1899, is but about one-third of the maximum 

 movement observed by Green in 1888 (August 13 to 25). The only way to 

 reconcile the two results is to suppose that Green's measurements were 

 made farther up the slope towards the cascade, where the movement is un- 

 doubtedly much greater than towards the nose. Messrs. Vaux placed a 

 ninth plate upon the nose of the glacier and had it under observation from 

 August I to August 20, 1899. The average daily horizontal motion for the 

 first two intervals between measurements was 5.9 inches and 5.0 inches. A 

 crevasse then formed, detaching the block carrying the plate, and the subse- 

 quent apparent motion was 2.8 inches and 2.7 inches daily. 



8. Frontal Changes. 



a. Recession data. Owing to the easy accessibility of the glacier and its at- 

 tractiveness to the ordinary visitor, we have more data from which to determine 

 the frontal behavior of the Illecillewaet than an}' of the other Canadian glaciers. 

 As has been noted, from the photograph taken in 1887 by the Messrs. Vaux the 

 position of the ice at that time, with reference to a large boulder, was detennined 

 and in 1898 marked conspicuously. In 1888 the margin of the ice was marked by 

 Green and the glacier was j^hotographed bj- Notman & Son, of Montreal (plate 

 XXX VI, figure i). Reference blocks were marked in 1890 and 1895 by interested 

 visitors. A visit was paid to the glacier September 3, 1897, by Albrecht Penck, 

 of Vienna, and a sketch made of the tongue of the glacier and its relation to the 

 lower moraines. This was published in the Zeitschrift des Deutschen mid 

 Osterreichischen Alpenvercins, Jahrgang 1898, Band xxix, s. 55, under the title 

 "Der Illecillewaetgletscher im Selkirkgebirge. ' ' The height of a number of points 

 was determined by an aneroid and four reference blocks established and located 

 upon the map. These blocks were left to be marked b}^ a railroad employee, 

 but were apparently neglected and in 1904 could not be identified with absolute 

 certainty, owing to the changes in the ice margin. Based upon the railway 

 elevation at the station, Penck determined the elevation of the nose in 1897 as 

 4,793 feet (1,461 meters). The foot-bridge, just beyond the modern terminal 

 moraine he gives an elevation of 640 feet above that of the station, or above sea 

 level 4,760 feet, ' and this he uses as his datum for elevations about the glacier. 

 The nose of the glacier at this time lay ^^ feet above the floor of the bridge, and 

 the crest of the adjoining lateral just opposite was 131 feet above the valley 

 floor at the nose. 



In the year 1 898 a number of reference blocks and range lines were established 

 by the Messrs. Vaux and have since done excellent service in measuring the 

 frontal movements. In August, 1899, they made a very detailed survey of the 

 nose and adjoining region and prepared a large scale map which is of the greatest 



' The correction of the railroad levels reduces this elevation by 27 feet, giving the bridge-floor 4,733 

 feet. 



