tioned in passing, that there is strong reason for suspecting 

 the existence of an earlier glacial flood which overrode the 

 Half Dome, but its history is now so obscured that little is 

 known concerning it other than that it appears to have 

 been short lived as compared with the weaker but more 

 enduring later phase. 



It is almost certain from the appearance of the associated 

 topography, that at some recent date the streams of the 

 Upper Merced, the Tenaya, the Lower Merced, and the 

 Bridal Veil valleys all joined each other with accordant 

 grades. Along these older and moderately steep thalwegs 

 a set of activities has been operating in such a manner as 

 to have left the side valleys hung high above the main 

 valley base. And looking from Glacier Point (Fig. 4) the 

 result of such activities has been an enormous interruption 

 of the recent valley bottom (as indicated also in Fig. 3 taken 

 from a point near Inspiration Point) to the Little Yosemite 

 and the Upper Tenaya valley floors. 



And not only for the Yosemite but also for the valleys 

 generally of the High Sierras, one V-shaped valley has been 

 excavated in the floor of another similarly shaped valley. 

 In the case of the Yosemite it is the knobs and shoulders 

 above the Royal Arches, the rock projections under the 

 Half Dome as well as those under Clouds' Rest (Figs. 3 and 

 5) which indicate the remnants of the old floor below which 

 the present mighty "steps" and " tread" have been made. 

 A study of Figures 5 (a) and 5 (6) suggests that the glacia- 

 tion of the Yosemite was imperfect, the trough-like appear- 

 ance of matured glaciation is not present. The Upper 

 Evolution and the Tuolumne Valleys afford additional 

 examples of valley-in-valley structures, both upper and 

 lower valley being practically spurless, flat-bottomed in 

 places, dotted with basins or meadows and possessing a 

 wealth of Hanging Valleys, with the lower valley floors 



