184 EXPLORATION OF THE CANONS OF THE COLORADO. 
above and the horizontal beds below, unbroken ; the flexure is complete, and 
we have a monoclinal fold, as represented in Figure 67. 
Still another variation is found. In the same vertical section we may 
sometimes see that a bed composed of a so'mewhat brittle material is broken 
so as to form a fault, while the bed above or below, composed of a more 
flexible material, is bent so as to form a fold, and thus a fault and fold will 
be represented in the same cross section as in Figure 68. Thus it is seen 
that the transformation of a fold into a fault may occur in two ways longi 
tudinally along the course of the fault, and vertically 'in the strata. 
The flexures, or monoclinal folds, also change in character, for the dip 
of the beds may vary greatly from two or three to ninety degrees and if 
we trace such a fold along its course, commencing at its transformation from 
a fault, we may find the flexure becoming less and less, until it can scarcely 
be detected by the eye, and then, perhaps, increase gradually into an abrupt 
fold, and then into a fault, reproducing, in some irregular way, the varieties 
of faulting above described. 
These faults run in lines approximately parallel, and divide the district 
under consideration into long belts, or blocks, and one edge of each block 
usually lies at the foot of an escarpment, the other at the summit of an 
escarpment. In examining the down-throw of these blocks, it is observed 
that the edge which lies against the foot of an escarpment has usually been 
thrown down much more than the opposite one, so that the blocks are tilted 
more or less. The relative amount of the downfall of these two edges is 
ever changeable. There are cases where the summit edge seems to have 
preserved its original position without down-throw, arid there are other cases 
where the summit edge seems to have fallen quite as much as the other. 
There is yet another change rung on these displacements. In some 
places the beds, at the edge of the table, lying against the foot of the escarp 
ment, are turned down, while farther back from the fault, toward the summit 
edge, the beds are approximately horizontal. This is represented in Figure 
70. Thus the long, narrow blocks, into which the country is divided by 
these displacements, are warped, or twisted. 
These faults and folds, thus ever changing in their characteristics, pro 
duce like changeable features in the topography of the country. A sharp 
