58 PEARL SHELDON 
thrust faulting with small displacement. These faults are numer- 
ous, occurring by the score in the shale beds, especially in the 
Hamilton shales. Often several may be seen in the height of a 
single cliff. Since these faults do not, as a rule, cross bedding 
planes the amount of movement is indicated only by the displace- 
ment of the joints, which are nearly at right angles to the faults. 
Whether or not this shows the total movement depends upon the 
Fic. 1.—Two faults in the Hamilton shales. The eroded horizontal line is the 
lower fault. The upper fault descends to the left. : 
relative ages of the joints and faults. Perhaps some faulting took 
place before the joints were formed. The displacement is usually 
between a fraction of an inch and seven or eight inches. Four to 
six inches is common and a single outcrop of a fault will sometimes 
show progressive variation through almost the entire range of dis- 
placement found in these faults. In other places the displacement 
is nearly constant for rods. 
