60 PEARL SHELDON 
wave cutting they appear as considerably eroded lines, sometimes 
worn into tiny caves. Figs. 1 and 2 show two of these faults in the 
cliff beside the bridge where the highway enters Ludlowville from 
the south. The photographs are of adjacent portions of the cliff. 
The lower, nearly horizontal, fault is eroded by the creek which is 
cutting the cliff. The upper fault, which has an unusually steep 
angle, has a fresh exposure and is therefore inconspicuous. The 
displacement along the upper line is shown by the head of the ham- 
mer. The movement has been such as to thrust the central wedge- 
shaped mass to the left and into the cliff between the upper and 
lower parts of the rock. 
The exact direction of movement in the horizontal faults of the 
Ithaca region was not determined. Something might be learned 
from the relative amount of displacement of the different sets of 
joints but this method might be subject to error because of differ- 
ence in the time of formation of the different sets. In the cases 
observed there was not a conspicuous difference in the displacements 
of the different sets, indicating that the direction of thrust made a 
fair angle with each set there present unless much of the movement 
took place between the times of formation of the different sets. 
The comparative behavior of the faults in soft and hard rocks 
is interesting. In the Hamilton shales is a hard encrinal layer a 
foot or two in thickness. This is shown in Fig. 3. It did not 
yield to pressure without breaking so readily as the adjacent shales 
and the exposures of this layer along the lake show faults every few 
feet. They soon die out after entering the shale. Fig. 3 is a 
photograph of two faults at locality 14, Fig. 7. The slipping sur- 
faces of the faults in this layer are much slickensided. The vertical 
displacement along these faults is from a fraction of an inch to 
three inches. 
At locality 14, Fig. 7, where the encrinal layer rises above water 
level, the strike of eight faults was found to vary from N. 7o° W. 
to due W. with an average of N. 76° W. At locality 39 in the same 
layer eight faults varied from N. 65° W. to S. 89° W., with an 
average of N. 72° W. The strike of the majority was from 20-25° 
north of west. At locality 9 where the encrinal layer passes 
beneath the lake level two readings were N. 86° W., two N. 84° W., 
