284 ELEMENTARY GEOLOGY 
The horizontal line at right angles to the dip, is 
called the strike (Fig. 163). This is the line which 
corresponds to the horizontal edge of the mclined book 
cover." On a pitched roof the inclination of the face 
of the roof corresponds to the dip, the ridge pole to 
the strike. Being horizontal, the strike is measured 
by compass direction; and as the dip is at right angles 
to this, its inclination is measured in degrees from 
SSS ANS 8 ‘ 
7 NN S 
\ NWN 
» NAS SN 
Fia. 163. 
Diagram to illustrate strike (AB) and dip (BC). 
the horizontal (0° for horizontal, and 90° for vertical). 
The direction of the dip is measured by compass, and 
it 1s one of two directions at right angles to the strike 
(Fig. 164). 
The Folds. In the course of their disturbance from 
the horizontal position, rocks are very often bent or 
1 Strike can be defined without reference to the dip as follows: it isa 
horizontal line in the plane of the bedding. 
