92 GLACIERS OF THE CANADIAN ROCKIES AND SELKIRKS. 



value in the determination of changes in progress ' (see plate xxxi) . The)^ have 

 very carefully located upon their map the reference blocks established by them- 

 selves and others, so that they may be readily found upon the ground. To their 

 untiring zeal and devotion to the cause we are very largely indebted for our 

 knowledge of the behavior of the Illecillewaet front since the year 1887. From 

 their reference blocks the writer took measurements in 1902, 1903, 1904, and 1905, 

 and in 1904 established four other reference stations about the side from which 

 to determine the marginal changes. 



There is reason for thinking that the glacier in 1887 was just completing a 

 rather prolonged halt at the younger of the frontal moraines described. That 

 it had not recently extended much beyond is proven by the size of the alder 

 bushes growing about the outer slope. That it had made a rather prolonged 

 halt at this line, either at this stage or a previous one, is shown by the size of 

 the moraine, which, with the small amount of debris carried by the glacier 

 would require a considerable time in building. From the early photographs -it 

 is seen that the glacier was much bulkier and broader at this stage and the slopes 

 about the nose much steeper, enabling the glacier to maintain well its position at 

 the moraine (plate xxxvi, figure i). During the year 1887 to 1888 it had begun 

 to withdraw from the moraine, as shown clearly in the Notman view just refeiTed 

 to and as indicated by the rocks blotched with tar by Green. The retreat began 

 somewhat gradually and attained its maximum between 1890 and 1900, averaging 

 for these ten years about 5 3 feet per annum. The average for the opening lustrum 

 of the century is 19.6 feet, the retreat being I'educed until it amounted to but 

 two feet for the year 1904-5. For the 18 years from 1887 to 1905, the horizontal 

 retreat from the Vaux reference block was 597.5 feet, or at an average yearly 

 rate of 33.2 feet. It should be noted, however, that this measurement is not 

 in a line with the main axis of the glacier. The available data concerning this 

 glacier are given in summarized fonn below. The measurements were taken 

 variously, most of them between the middle of August and the middle of Sep- 

 tember, so that the retreat assigned to some years, may belong in part to the 

 preceding, or the following year. 



Recession Data of the Nose of the Illecilleivaet Glacier. 



' " The Great Glacier of the Illicilliwaet," George and William S. Vaux, Jr., Appaladua, vol. ix, Mch. 

 T900, p. 156. 



