"There are at least two ways in which this state of 
affairs may have arisen, 
"First, the Greater arch may have been lifted so long 
before the Lesser that its waterways were carved too deeply 
to be diverted by the gentle flexure of the latter. The 
drainage of the Lesser would in that case be classed as 
antecedent. If the Lesser arch were first formed and carved 
the lifting of the Greater night throw a stream across its 
summit; but it could not initiate the waterways which skirt the 
slopes of the Lesser, especially if those slopes were already 
furrowed by streams which descended them. If the establish- 
ment of the drainage system depended on the order of uplift, 
the Greater arch is surely the older. 
" Second, the drainage of the Lesser arch may have been 
imposed upon it by planation at a very late stage of the de- 
gradation. Whatever was the origin of the arches, and what- 
ever was the depth of cover which they sustained, the Greater 
is certain to have been a center of drainage from the time of 
its formation. When it was first lifted it became a draina.ge 
center because it was an eminence; find afterward it remained 
an eminence because it was a drainage center. When in the 
progress of the denudation its dikes were exposed, their 
hardness checked the wear of the summit and its eminence 
became more pronounced. It was perhaps at about this time 
that the last of the Cretaceous rocks were removed from the 
summits and slopes of the two arches and the Flaming Gorge 
