- CURVATURE OF STRATA ie 
of the surface must affect the direction of the outcrops, which 
in such a case behave as contour-lines or lines of equal 
elevation, and follow all the irregularities of the ground. 
When strata are gently inclined, the outcrops are also strongly 

FIG. 13.—OUTCROPS CONCEALED UNDER BOULDER-CLAY, #4. 
affected by the shape of the surface, but this influence 
gradually lessens as the angle of dip increases, the outcrops, 
as the beds approach verticality, becoming more and more 
persistent in direction, and being less and less modified by 
changes in the form of the ground. When the strata are 

FIG. 14.—OUTCROPS CONCEALED UNDER OVERLYING STRATA. 
actually vertical or standing on end, the outcrops then run 
in straight lines across hill and dale, being practically inde- 
pendent of the surface features. 
A little consideration will show that the dveadth or width 
of an outcrop must similarly be influenced by the angle of dip 

FIG. 15.—WIDTH OF AN OUTCROP AFFECTED BY ANGLE OF DIP. 
and the form of the ground. In the case of horizontal beds, 
the uppermost stratum, although it may be quite thin, must 
frequently occupy a relatively wide area and form a broad 
outcrop. With inclined strata, it is obvious that the outcrops 
will be broad or narrow according as the dip is low or high— 
tect i i ere et 

