GLACIAL EROSIOX AXD TRANSPORTATION. 273 



interiors of some of the amphitheatres are terraced in the same 

 manner as are the bottoms of the canons leading from them, a 

 feature which has been observed in the cirques of the Rocky 

 Mountains as well. Nearly all the various branches of the 

 ancient glaciers of the high Sierra headed in deep recesses of 

 the character above described. In places the cirques occur on 

 either side of a fragment of table-land, and have been eroded 

 back until only a knife-edge of rock, so narrow and broken 

 that the boldest mountain-climber would hesitate to traverse 

 it, is all that divides one profound depression from another. 

 Examples of this nature are common about Mounts Lyell 

 and Ritter, and find a number of typical illustrations in the 

 cliffs of the Kuna and Koip crests. At the head of Rush 

 Creek are a number of separate cirques, each holding a gem- 

 like lakelet, in which the various branches of the stream drain- 

 ing the basin have their source. Silver Creek heads in a 

 magnificent amphitheatre formed by the union of several 

 cirques, which during the height of the Glacial epoch was 

 completely filled with neve. On the south side of Kuna and 

 Koip peaks are two vast amphitheatres which rank among the 

 finest in the Mono region. ... No topographic delineation or 

 word description can convey the impressive grandeur of some 

 of these vast, shrine-like recesses that have been sculptured 

 during the lapse of centuries from the rugged cliffs of the high 

 Sierra. 



In general the cirques open northward, but many excep- 

 tions to this rule can be found, especially about the head-waters 

 of Rush and Silver Creeks. 



It is in the cirques about the higher peaks that living 

 glaciers are still found, and those not harboring perennial ice 

 are deeply filled with snow during a large portion of the year. 

 The slow melting of the snow and ice in these reservoirs feeds 

 the rills which join one with another to form the creeks flow- 

 ing into Lake Mono. The balance between the climatic con- 

 ditions favorable to the existence of glaciers and those which 

 insure their disappearance is here nicely adjusted, and, should 

 the equilibrium shift to the side of greater congelation, these 

 ancient cirques would be the first points to exhibit the changed 

 conditions. They were the fountains which gave birth to the 



