476 SIMGIOIMES JHOME SA ULOVEIN TCS 
ding, and the two do approximate but not exactly accord in 
direction upon the limbs of the folds, a close examination 
shows that on the crests of the anticlines and in the troughs of 
the synclines the two structures intersect each other. 
ar {2 
og AN: 
FIG. 9 
Fics. 8 and 9. — Diagram showing development of fissility along the longer and 
shorter diagonals of a deformed portion of a rock stratum. 
In the center of stratum the fractures are in the planes of greatest shearing, but 
onthe outside of the layer the fractures are in lesser shearing planes, the direction of 
fracture being controlled to some extent by bedding. 
At the beginning of the process it may be noted that the 
shortening is at right angles to the bedding. At the end of the 
process the shortening is parallel to the bedding. Thus the 
work first done is partly undone. The resultant position of the 
shorter axes of the mineral particles in reference to the bed is 
intermediate between the two extremes. 
DEVELOPMENT OF FISSILITY IN HETEROGENEOUS ROCKS. 
The development of fissility in heterogeneous rock beds is 
still more complicated. The directions of the forces are exactly 
the same as with cleavage, but as fissility develops along the 
shearing planes, in the simplest case this structure forms in two 
