462 AXIS — DISLOCATIONS AND DENUDATION OF TORTWORTH. 



is full of vertical joints and fissures. That the direction of these joints (many of which 

 have slickenside surfaces) , has been caused by the same operation which produced the 

 great anticlinal, there can be little doubt ; for the dominant planes are parallel to the 

 strike of the Old Red Sandstone. This ridge finally subsides at its west-south-western 

 end, by sinking on two sides beneath the limestone. 



In conclusion it may be remarked, that vast masses of the overlying formations of 

 New Red Sandstone, Lias, and Inferior Oolite, must have been removed by the powerful 

 denudations which doubtless, both accompanied and followed the intrusion of the trap 

 rocks and the dislocations of the strata ; for as soon as we quit the small arena of agi- 

 tation around Tortworth, and recede from the proximity of rocks of igneous origin, the 

 overlying formations resume their regular positions. (See Map.) We may further con- 

 clude, that volcanic rocks, either rising to the surface or struggling to emerge, threw 

 up the band of elevated Silurian rocks which has been traced in an anticlinal form from 

 the Valley of Woolhope to Alveston Down, near Bristol. 



