'372 EEPORT UNITED STATES GEOLOGICAL SURVEY. 



but instead of choosing the latter and apparently easier course, it pene- 

 trates the rocky strata of Escalante Hills with persistency, leaving un- 

 touched the basin which lies but a very short distance from the river. It 

 can hardly be otherwise but that the present river channel is antecedent 

 to the surrounding uplifts or structure, and that the basin alluded to has 

 been caused by erosion of comparatively more recent date. The latter 

 question, however, pertains more to the duty of the geologist, who in this 

 case has no doubt arrived at a similar conclusion. 



Near tbe junction of the Yampa and the Green River lies a small park- 

 area, named Echo Park in previous explorations of this river by Major 

 Powell and leaving this park the stream, now called Green Eiver, soon 

 enters a precipitous canon and remains in it for Smiles, passing afterward 

 through Island Park in large curves, after which it is again buried 

 between the huge canon cliffs of Split Mountain, within which the 

 stream remains for 5 miles before if emerges, at last, into the Wonsits 

 Vallev. The height of the canon walls along Yampa River vary from 

 1,000 "'to 1,500 feet, and those of the Green River from 2,000 to 2,500 feet. 



