A TOPOGRAPHIC FEATURE OF THE HANGING 

 VALLEYS OF THE YOSEMITE. 



The larger hangjng valleys around the Yosemite valley have 

 topographic features in common that are interesting in them- 

 selves, and they likewise afford some evidence in regard to the 

 comparative cutting powers of ice and water. 



When formerly I used to look up from the valley below at 

 the Upper Yosemite fall, I always wondered 

 what kind of topography there could be up 

 on top to cause Yosemite Creek to come 

 over the rim of the valley at an elevation 

 much higher than the gorge just east of 

 it — the gorge through which the trail to 

 Eagle Peak passes. A glance at Fig. 4 will 

 show what is meant. That topography was 

 explained during a recent visit to the 

 Yosemite, when I had an opportunity to 

 see the valleys above some of the falls. 



The Illilouette fall is not quite at the 

 head of the canyon ; the canyon passes by 

 or overlaps the creek so that the creek enters the canyon on its 

 east side, as shown in the accompanying sketch. (Fig. i.) 



At the Nevada fall this overlapping of the canyon below by 

 the stream above the fall is still more marked, although, owing 

 to the choking up of the head of the gorge, it does not attract 

 one's attention so promptly. The trail leading to the top of the 

 Nevada fall passes up through this side gorge. 



At the Vernal fall again the gorge below extends up past the 

 fall, though the overlap is only short in this case. 



The explanation seems to be the same for each of these forms. 

 Take first the Illilouette fall : the South Canyon Creek, or 

 Illilouette Creek, which forms the Illilouette fall drains a large 

 area, especially on the south and west side of the stream. 

 Toward the close of the glacial epoch, when the main Yosemite 



547 



Fig. I. — Sketch show- 

 ing how Illilouette Fall 

 enters the gorge at the 

 side. 



