﻿494 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 47 



growth is here 1.14 mm., as compared with .884 mm. in the Lake 

 Louise valley. Some exceptionally large spruces and hemlocks are 

 found at the entrance to the Asulkan valley, two of which, by calcula- 

 tion, appear to be 525 and 598 years of age. Toward the head of the 

 valley the trees become smaller and younger and the rings of growth 

 somewhat coarser. It is about two miles from these trees up to 

 where the Asulkan brook enters the narrow valley and has excavated 

 some 30 to 40 ft. of schist since the retreat of the glacier. One of 

 the largest firs here shows 161 rings of growth and a still larger 

 hemlock near is not far from 250 years of age. So far as such data 

 can be depended upon, it would seem that the Asulkan withdrew up 

 this portion of the valley in about 350 years and at an average rate 

 of 30 ft. a year. From the schist cut to the present nose of the 

 glacier the valley opens and for this quarter mile the rate would pre- 

 sumably be less, perhaps not more than one-half or one-third as great, 

 owing to the greater mass of ice to be melted away. Similarly the 

 retreat from the outermost block moraine into the narrower portion 

 of the valley would also probably be slow. 



VI. Significance of the Block Moraines 



Since this entire report is simply a summary of the most important 

 observations made no resume in closing need be attempted. It is 

 desired, however, to point out here what seems to the writer, in his 

 present state of knowledge, to be the significance and importance of 

 this special variety of terminal moraine. While in the field they were 

 a perplexing puzzle and not until the snow-clad Rockies had dis- 

 appeared upon the western horizon did even a plausible explanation 

 present itself. The theory of their formation will need to be tested 

 by observations in many of the valleys adjoining those studied. As 

 has been pointed out they are made up of very coarse fragments of 

 the surrounding cliffs and peaks, the actual size of which is not so 

 remarkable, knowing what a transporting agent a glacier is, as the 

 average size of the fragments composing the moraine. The finer 

 materials, commonly present in a terminal moraine, are completely 

 overshadowed by these massive blocks and such fine material was 

 apparently not present from the first. These blocks were carried 

 on or in the ice, not beneath nor pushed ahead and appear to be in 

 a double series in four of the five glaciers selected for study. None 

 of the glaciers observed could now make such a moraine, no matter 

 how prolonged the halt. Periods of excessive weathering would 

 certainly load the glacier with much fine, as well as coarse material. 

 The prevalence of the phenomenon prevents our resorting to the 



