
512 GEOTECTONIC (STRUCTURAL) GEOLOGY. [Boos IV. _ 
to 2 feet, and the diminution would continue until, when the bed was — 
on end, the breadth of the outcrop would, of course, exactly correspond 
with the thickness of the bed. It is further to be observed that. 
among yertical rocks the direction of the outcrop necessarily cor- 
responds with the dip, and continues to do so irrespective altogether 
of any irregularities of the ground. The lower therefore the angle of 
inclination the greater is the effect of surface inequalities upon the 



Fic. 230.—Sinvous Ovrcorors or HorizonrTaL STRATA DEPENDING ON INEQUALITIES 
OF SURFACE. 
The wavy black lines mark the outcrops of successive conformable horizontal beds, 
line of outcrop; the higher the angle the less is that influence, till 
when the beds stand on end it ceases. 
Strike.—A line drawn at a right angle to the dip is called the 
Strike of the rocks. From what has just been said this line must 
coincide with outcrop when the surface of the ground is quite level as 
on the beach in Fig. 231, and also when the beds are vertical. At 
all other times strike and outcrop are not strictly coincident, but the 
latter wanders to and fro across the former according to changes in 
the contour of the ground. ‘The strike may bea straight line, or may 
curve rapidly in every direction, according to the behaviour of the 
