
FAULTS 167 
tion, or with some in one direction and some in another, 
often occur in our coalfields, where they are known as step- 
faults—an appearance shown in the diagram (Fig. 45). Such 
FIG. 45.—STEP-FAULTS, 
faults, when their downthrow is in the same direction as the 
dip, have the effect, as already indicated, of preventing certain 
beds from croping out at the surface. On the other hand, 
a succession of step-faults, each with its downthrow against 
Fic. 46.—STEP-FAULTS HADING AGAINST THE DIP. 
the dip, may cause a coal-seam to crop out again and again. 
(See Fig. 46, which should be compared with the models in 
Bis. At.) 
When parallel or approximately parallel faults hade 

FIG. 47.—TROUGH-FAULTS AND RIDGE-FAULTS. 
towards each other, they produce the phenomena of trough- 
faults (Fig. 47,77). When they hade away from each other 
