DEFORMATION OF ROCKS 331 
folds, the secondary folds on the limbs are seen to be inclined. 
In reference to a primary anticline, the axial planes of opposite 
folds converge downward; in reference to aprimary syncline, the 
axial planes of opposite folds diverge downward, but both less 
than they would were it not for readjustment. The above experi- 
ment does not exactly represent the conditions in nature, for the 
accommodations between the beds, instead of occurring parallel 
to the primary folds, would take place parallel to the secondary 
folds. However, an examination of the distortion of the axial 
planes of Fig. 15, shown in Fig. 16, shows beyond question that 
Fic. 16.— The same, as it was distorted when folded into anticlines and synclines. 
when a set of beds is folded which are free to adjust themselves 
parallel to bedding, the movement of the material in the upper 
half of the beds is relatively away from a syncline toward an anti- 
cline, and the movement of the lower half is away from an anticline 
toward asyncline; or,stated more generally, the differential move- 
ment between any two adjacent beds on the legs of folds is rela- 
tively up in the higher bed and relatively down in the lower bed. 
It cannot be doubted that the sum total of the readjustments 
between the beds, although they follow the crenulations instead 
of being exactly parallel to the primary fold, would give the 
same effect. Therefore there is a tendency in anticlinoria and 
synclinoria, due to normal differential movement, for secondary 
folds to become inclined, taking the radial planes of the primary 
folds as axial planes of the secondary folds. However, when 
the readjustment is uniformly distributed this tendency does not 
so far affect the secondary folds but that they fall within the 
class of normal composite folds. But if the major readjustment 
of a great set of formations were largely concentrated along a 
