deposited in terrace form as the Merced Glacier decrease, I 

 in size, and they were crowded over toward the Little 

 Yosemite (See also Fig. 15). Such features evidence the 

 shrinkage of the lateral measure of glacial strength. Then 

 ensued the dropping of moraines near El Portal, and still 

 later at El Capitan. Still later, the polished pavements of 

 Lake Tenaya and the Merced were formed by the gradual 

 obliteration of huge grooves, as the heavier ice action was 

 gradually replaced by the weaker sand-papering action 

 of the dying glaciers. At the same time the walls of 

 Yosemite showered talus on to the huge "tread" of the 

 Yosemite, and the water streams of the melting ice gradu- 

 ally filled up the depressions on the "tread," and converted 

 the whole floor into a great "meadow." In this way the 

 talus and the moraines were in part buried. The bulk of 

 the morainic material had however been crushed to boulders 

 pebbles and mud in the down stream constrictions and 

 swept away later by the water Hoods. 



The depth of alluvium in the Yosemite Valley is doubtless 

 not great, as it merely marks the aggradation of a "tread" 

 which had been formed rapidly as the result of "step" 

 recession, and therefore differs from a fiord basin which 

 has been excavated at the foot of a declivity and near a 

 decided valley constriction. 



The lack of typical cirque forms in the Tenaya Gorge 

 and at the Nevada and Vernal Falls is due to the heavy 

 action of the ice in descending the "steps" of recession, 

 such action completely modifying the amphitheatrical form 

 which is mainly the expression nf sapping agencies. 1 To see 

 the typical einpieone must ascend the Tenaya, the Merced, 

 or the associated San Joaquin Valleys, to the glacial head 

 waters where one may see the amphitheatres encroaching 

 on each other and each exhibiting more or less the atmos- 



1 "Comision by (ir.ivity Streams," Appendix II. 



