AN EXCURSION to the YOSEMITE (California), or 



Studies in the Formation of Alpine cirques, 



"steps," and valley "treads." 



By E. O. Andrews, b.a., Department of Mines, Sydney. 



[Read before the Royal S< ty / T. S. Wales, August 3, 1910.] 

 Table of Contents. 



2. The psychological factor in the history - r ti < glacial contro- 

 versy, (a) The prejudice of environment, (b) Lack of imagina- 

 tion a hindrance to progress. 



3. Topography of the Yosemite Locality. 



4. Mechanics of Stream*. — Lateral, vertical and longitudinal 

 measures of stream strength. Energy. Work. Locations of 

 maximum stream corrasion. Abrasion and quarrying. Roches 

 moutonnees. Analogy of specimen collector. Form and shape 

 of channel determined by strength and size of stream. 



5. Yosemite profiles.— -Increase of glacial velocity near El 

 Capitan. Basin and "step" formed there. Headward recession 

 of "step" by sapping and quarrying. Bridal Veil Falls formed. 

 Basin formation less emphasised as "step" carried up stream. 

 Yosemite Falls formed. Glacial surface sinks from summit of 

 El Capitan Dome to point 1,500 feet lower. Ice Fall formed near 

 Half Dome. Upper portions of Yosemite Wall sapped. Formation 

 of mighty "steps" in Tenaya under Clouds' Rest and Liberty 

 Cap. Cessation of Ice Age. Glacial decadence. Baring of 

 cirque walls. Sapping under atmospheric agencies and tendency 

 to establish slope of repose. Moraines deposited in old cutting 

 curves under Clouds' Rest. Aggradation of Yosemite "tread" to 

 form a meadow. Obliteration of deep ice grooves by later ice 

 polishing near Tenaya Lake. 



