570 proceedings of the academy of [dec, 



Illecillewaet Glacier. 

 Glacier House, British Columbia. 



Being the most accessible of any of this group, the Illecillewaet 

 Glacier has been observed yearly since 1898. Prior to that time, 

 beginning in 1887, the observations have been made with less regu- 

 larity.^ 



The work may be divided under three heads, each of which will be 

 treated separately as follows : 



Test Pictures. — These have been made each year, beginning 

 August 17, 1898, from the marked rock "W." From this point a 

 complete view of the tongue and lower glacier may be had, and of a part 

 of the icefall almost up to the limit of the dry glacier. The same 

 camera and lens being used and exactly the same position selected, the 

 pictures indicate very accurately the changes which have taken place 

 in any given interval. A careful study of these shows that in spite of 

 the continued recession of the tongue and a general shrinkage of the 

 ice at the edges, particularly at the left side where great masses have 

 broken away uncovering water-worn bedrock, the thickness of the ice 

 at the sky line is appreciably thicker than it was in 1898. This condi- 

 tion has been noted for a number of years, and time alone will prove 

 whether an advance will take place when the thicker mass reaches the 

 icefall and tongue. There is no doubt, however, that in all other par- 

 ticulars — breadth, depth and extension of tongue — the glacier is at 

 present from year to year decreasing. A comparison of the two test 

 pictures of 1902 and 1906, reproduced herewith, with that made in 1898 

 (compare Plate V, Proc. Acad. Nat. Sci. Phila., 1899) will show in 

 detail the changes which have taken place. 



'p Recession of Tongue. — As previously noted (Proc. Acad. Nat. Sci. 

 Phila., 1899, p. 124), the first accurate location of the tongue of the ice 

 is to be found in a long flat boulder not far from the moraine of 1887 

 (S. on the map), lettered by unknown hands, ''16 feet to nearest ice, 

 '90." With this rock as a basis the glacier showed a retreat after 

 eight years on"August 17, 1898, of 452 feet. 



From 1898 to the past summer (1906) the annual change has been 

 determined from a rock (marked "C." on map) lying in the centre of 

 the bed moraine and which on August 17, 1898, was 60 feet from the 

 tongue of the ice. The following table shows the recession each year 

 and the date on which the measurements were made. 



' ' ForTdetailed accounts of pre\aous investigations on this glacier see Proc. 

 Acad. Nat. Sci. Phila., 1899, pp. 121 and .501, and 1901, p. 213. 



