GLACIER OF MT. ARAPAHOE, COLORADO 649 



the illustration Fig. 1. The peak with its perpendicular cliffs 

 forming the south wall, together with about one third of the 

 cirque, is cut off from view by the bluff in the foreground. Fig- 

 ure 2 is a near view of this peak showing the upper extremity 

 of one of these arms of snow and ice. 



The cirque presents exceptional advantages for the accumu- 

 lation and preservation of snow and ice : 



1. The encircling peaks and ridges are barriers behind which 

 the drifting snow accumulates during the winter. From whatever 

 direction the wind blows, except from the northeast, its velocity 

 is checked by the peaks and ridges forming the walls of the cirque, 

 and the cirque receives its burden of snow. The importance of 

 this mode of accumulation is well illustrated in the long snow 

 drifts which are common along the high ridges throughout the 

 mountains where the winds have dropped their burden in the lee 

 of the crests. In some instances the summer's heat is not suffi- 

 cient to melt away these drifts even where they lie exposed to 

 the sun on the south side of the ridges. 



2. The snow and ice of the cirque are more or less protected 

 from the heat of the sun, by the elevated rim which is highest, 

 and the inner slope steepest, on the south and west sides. On 

 these two sides where the slope is gentle enough to permit it, 

 lie accumulations of snow and ice of unknown thickness, extend- 

 ing from bottom to top of the walls. On the northern side, i. e., 

 the southern slope of the spur, the snow and ice reach but a little 

 way up the side. This may be due in some measure to a differ- 

 ence in the amount of accumulation of snow, but it is certainly 

 due primarily to the greater melting power of the sun on the 

 slope facing southward. 



3. The snow and ice of the cirque are also protected by 

 sheltering from the east, south, and west winds. While our 

 party was on one of the peaks overlooking the cirque, a thunder 

 storm from the southwest enveloped the mountain. After the 

 wind had swept the clouds from the southwestern side of the 

 mountain, the cirque remained full of thick mist. The wind 

 which was blowing at a moderately high rate of speed, cut off 



