30 SHRINKAGE FISSURES OLDER ROCKS. 



debris will probably be removed by rain and runnels 

 as fast as it is formed. Consequently the fissure will 

 not only be kept open, but also enlarged, the denu- 

 dation generally acting more in depth than width. 

 The consideration of denudation would, however, lead 

 us away from the present portion of our subject; 

 and prior to entering into that, we must describe 

 more fully the connection between master joints and 

 faults. 



