464 J.W. Powell— Geological Structure of the Grand Cation. 
Of the second order we also have three varieties : 
A, anticlinal valleys, which follow anticlinal axes ; 
B, synclinal valleys, which follow synclinal axes; 
, monoclinal valleys, which run in the direction of the 
strike between the axes of the fold, one side of the valley 
meagre term of comparison for the sum of the material which 
has been carried away by rains and rivers. : 
On the flanks of the folds which are found everywhere 2 
the valley of the Colorado, we see the edges of formations 
which once, doubtless, extended quite over the folds. That 
these formations were once continuous appears evident from 
the following considerations: first, they are not seen either to 
thin out, or thicken up, and bear no evidences of having been 
immediate shore formations; second, they terminate in abrupt 
escarpments; third, they may be traced on either side of the 
_ folds, and seem to have the same lithological and paleontolog!- 
____ gal characteristics; and fourth, outliers of the formations may 
be discovered in many places, that have withstood the vicisst 
