100 National Geographic Magazine. 
along the strike of the soft beds and square across the strike of — 
the hard beds. Middle Brook, at the southern bend of First 
mountain near Bound Brook (B, B), presents the peculiarity of 
branching east and west while on the trap sheet of the mountain : 
this may be due to a retention here, where the dip is moderate, of 
an initially superimposed bifurcation ; or to guidance by fractures 
at this point where the course of the mountain changes rather 
abruptly ; the facts at hand do not serve to make choice between 
these alternatives. 
The lesson of greatest importance in this study lies, to my mind, 
in the gradual development of accordant subsequent streams in a 
region where the unchanged superimposed drainage would show 
no such accordance. Similar adjustment of subsequent streams 
to structural features may characterize drainage systems that 
were originally antecedent: and with this principle in mind, I 
have recently read over with renewed interest Powell’s classic 
study of the Green river where it crosses the Uinta mountains.* 
The Green river and the smaller streams of its lateral cations and 
valleys are all regarded as antecedent. Let us examine the argu- 
ments on which this conclusion rests. 
The Green river itself rises many miles north of the Uinta 
range, traverses a relatively low basin before reaching the flank 
of the mountains, and then instead of turning away, it boldly en- 
ters the great uplift and trenches it from side to side in a pro- 
found cajion, flowing out to the southwest on its way to the Colo- 
rado. There is relatively low ground at the eastern end of the 
range, several thousand feet lower than the summits of the range 
on either side of the Green river cafion, and many thousand feet 
lower than the restored crest of the great uplift ; but the river 
does not follow this open round-about course. Powell says that 
the river cut through, instead of running around, the great ob- 
struction, because it “had the right of way; . . it was running 
ere the mountains were formed.” Had the mountain fold been 
formed suddenly, it would have turned the river around it to the 
east ; “but the emergence of the fold above the general surface 
of the country was little or no faster than the pregress of the cor- 
rasion of the channel? .. . . . “The river preserved its level,. 
but the mountains were lifted up. ... . The river was the saw 
* Exploration of the Colorado river of the west, Washington, 1875. 
152-166. See also the geological map in the Geology of the Uinta 
mountains, 1876. 
