EXTINCT AND EXISTING GLACIERS OF COLORADO 6 1 



hergschrund and the crevasses are exceedingly fine when viewed in late 

 August and early September. Exaggerated stories have been current 

 as to the depth of the ice and the depth of the crevasses. The contours 

 of the cirque indicate plainly that the greatest depth of the ice can be 

 scarcely, if any, more than loo feet. I have examined nearly all of 

 the larger crevasses upon repeated visits late in the season when they 

 were free from snow and most accessible, and have found them to 

 run from 30 to possibly 60 feet in depth — though I have not yet 

 measured any which reached the latter depth — and many of them 

 quite evidently reach the bed of the cirque in places, showing that 

 the ice has no such depth as is commonly supposed. 



The moraine at the foot of the ice-tongue is found each season 

 covered with fine glacial mud mingled with rock fragments of all 

 sizes. The streams issuing from beneath it, and the first lake below, 

 are milky white with "rock-flour." As the water flows through 

 successive lakes the sediments gradually settle and the color disappears 

 long before the water reaches Silver Lake. The ice has the granular 

 structure of tj^ical glacier-ice. 



The stratification of Arapahoe has been described by Fenneman. 

 The blue bands are finely seen in some of the crevasses. On the 

 surface of the ice little ridges caused by unequal melting of alternate 

 bands catch the dust blown upon the ice, and thus make the banding 

 appear even more prominent than it is. 



To determine the rate of motion, Mr. Watts and I set a line of 

 ten zinc tablets across the face of the ice on August 30, 1904, tying 

 them accurately to bench marks upon the granite walls of the cirque 

 and upon the terminal moraine, by triangulation and direct observa- 

 tion with instruments. Zinc tablets were used because they at once 

 melt into the ice and thus avoid sliding. No. i was placed 300 feet 

 from the northeast edge of the ice; from No. i to No. 2, 89 feet; No. 

 2 to No. 3, 51.7 feet; No. 3 to No. 4, 58.6 feet; No. 4 to No. 5, 65.4 

 feet; No. 5 to No. 6, 82.8 feet; No. 6 to No. 7, 84.4 feet; No. 7 to 

 No. 8, 73.8 feet; No. 8 to No. 9, 97.2 feet; No. 9 to No. 10, 114 -4 

 feet; making the last tablet 1,017.3 feet from the north edge of the 

 ice, nearly at the center. On August 30, 1905, we again visited the 



