Page:The Selkirk mountains (1912).djvu/179

Rh right-hand moraine about 1,000 feet above the snout of the glacier, a transit-theodolite set up at each end, and readings taken to each plate. A base also of 334 feet 6 inches was measured on the ground moraine in front of the forefoot and a number of points fixed by readings from both ends. In addition, the relative positions of a number of marked rocks, and rocks for future reference were located. (See map.)

As a result of observations made at intervals from 1899 to 1906, it has been computed that the average greatest daily movement of the ice down its bed, is 5.9 inches, or 179.4 feet per year.

On the map, directly in front of the most advanced portion of the ice-forefoot, will be noticed a rock marked "C". From this rock yearly measurements have been made to the nearest ice. The table below shows the annual recession from 1898 to 1910.

Illecillewaet Glacier—Recession of Tongue of Ice from Rock "C".

The Asulkan Glacier.

Observations taken on the Asulkan Glacier by the Messrs. Vaux were on the same lines as those on the Illecillewaet, but they have not been continuous and no attempt was made to measure the rate of flow until 1906. In 1901 there was a distinct advance which continued for about three years when recession began again. This advance interfered with the observations, the large boulders in the moraine marking the datum-line being shoved forward by the advancing ice and entirely obliterating the base-line used for measurements.

The average greatest daily motion of the ice has been computed at 6.7 inches, or very nearly 204 feet per year. It was found on the 21st August, 1909, that the advance had been so great as to obliterate the marked rocks that had been used since 1899.

The Illecillewaet and Asulkan Glaciers are the only two on which measurements and observations have yet been taken, owing, no doubt, to their accessibility from Glacier House. Many glaciers of approximate magnitude difficult of access, offer most interesting studies, among them the Bonney, Rogers, Geikie, Deville, Grand, Beaver and Duncan Glaciers.