108 GLACIERS OF THE CANADIAN ROCKIES AND SELKIRKS. 



of rock had been deposited the Asulkan began to retreat, withdrawing a distance 

 of 3,500 feet up the Asulkan Valley. The front now halted and there was built 

 a moraine of the ordinary type across the valley, consisting of fine and coarse 

 material, intermingled with but few coarse blocks. From this we conclude that 

 the glacier was, at this time, carrying the ordinary kind of load. The retreat was 

 resumed and in the meantime the glacier became a second time laden with coarse 

 fragments of the adjoining cliffs. At a distance of about 1,000 feet from the 

 previously formed moraine these blocks began to be deposited and were dropped 

 over a distance of some 500 to 600 feet, not so concentrated or imposing as the 

 outer bear-den moraine. For the next 1,500 feet these blocks were scattered 

 along the valley, implying that the supply over the surface had not been suf- 

 cient to bring about a halt. The retreat continued towards the head of the 

 valley and at a distance of 2,000 feet farther a halt occurred and a moraine of the 

 ordinary type was again built, with the usual quota of fine and coarse material. 

 From the time then that the Asulkan was about to separate from the Illecillewaet 

 it became twice loaded with coarse, angular fragments of quartzite, building a 

 moraine of the bear-den type. In the interval it carried material of the ordinary 

 kind found upon and within the ice and built a moraine of the ordinary type. 

 Subsequently to the formation of the second, straggling, bear-den moraine, it 

 has been carrying and depositing the usual class of material. It differs from 

 the Victoria in that the ancient moraine of the ordinary type was deposited 

 between the two bear-den moraines instead of outside the two, as in the case of 

 the latter. 



c. Rate of retreat. The only possible data for any estimates upon the rate 

 of retreat up the valley must be drawn from a study of the forest trees and no 

 one realizes any more strongly than the writer how unreliable and misleading 

 such data may be. However, we may obtain an approximate minimum estimate 

 by this means, which may have some interest, if not real value. Some excep- 

 tionally large spruces and hemlocks are found near the mouth of the valley and 

 within the outer bear-den moraine. Based upon the average thickness of the 

 rings of growth, noted upon page 96, two of the largest seen should be 525 and 598 

 years of age, respectively. Toward the schist cut, at the head of the valley, the 

 rings of growth become coarser and the trees smaller, the difference in elevation 

 amounting to about 900 feet. One of the largest firs showed 161 rings of growth 

 and a still larger hemlock growing near was estimated to have lived about 250 

 years. Assuming that it required about the same length of time for the trees to 

 get started at either end of the valley, it took the Asulkan about 350 years to 

 retreat the two miles from the mouth of the valley to the schist cut, or at the 

 average rate of about 30 feet a year. From the schist cut to the present nose, 

 about one-quarter mile, the valley opens and the retreat must have been much 

 slower, owing to the volume of ice to be melted away. If we assume that it 

 required 50 years for the hemlock noted to get started, the minimum time in- 

 volved would be 300 years and the maximum average rate of retreat for this part 

 of the glacier would have been about 4.4 feet per annum. If the cut in the schist 



