DEFORMATION OF ROCKS 475 
rotated so as to be almost parallel to bedding, but usually is 
somewhat steeper. As the resultant differential movement is 
comparatively slight on the steeper, shorter limb, the cleavage 
usually cuts across the bedding at a considerable angle and is 
steeper in reference to the horizon. On the opposite limbs of 
monoclinal fan-shaped anticlines the cleavage may be nearly 
parallel, or may even converge downward, and on the opposite 
limbs of monoclinal fan-shaped synclines the cleavage may be 
nearly parallel, or even diverge downward. 
This contrast with symmetrical folds is due to the continu- 
ous rotation in the same direction of the cleavage along the arch 
limb of the fold combined with the rotation in the reversed limb, 
first opposite to and afterward in the same direction as that on 
the arch limb. As in the case of symmetrical folds, the vari- 
ation in dip of cleavage is less than the variation in the dip of 
bedding. In districts in which cleavage and bedding have the 
relations above described, on the longer arch limbs it is often 
difficult to discriminate between the two, but it is believed that 
the cleavage is usually slightly steeper than the bedding, as 
already explained. On the steep or reversed limbs the minor 
crenulations of the strata are usually easily detected intersect- 
ing the cleavage. 
When rocks are openly folded the discrepancy between 
cleavage and bedding is usually great. As the folding becomes 
closer the average discrepancy becomes less. If the compres- 
sion goes so far as to form isoclinal folds the bedding and cleav- 
age may nearly correspond upon the limbs of the folds, but the 
two will be at right angles to each other upon the crests of anti- 
clines and in the troughs of synclines (Fig. 7). When the 
compression is so great as to form plicated folds, the changes 
in the direction of bedding being very sharp, the discrepancy 
between bedding and cleavage will be slight. However, the 
discrepancy is real and important. The cleavage in this case 
may be about parallel to the axial planes of the folds, and will 
cut the beds at avery acute angle. In many districts where 
cleavage has been described as everywhere according with bed- 
