486 GEOLOGY OF THE SOUTH EAST OF DORSETSHIRE. 



town, eaten a deeper and deeper bed vertically down by its 

 own mighty powers ? If it has not accomplished such a pur- 

 pose, what is to be said of the solvent powers of our English 

 rivers, that have, without any display or any thunder, chisel- 

 led out such enormous gorges and ravines, many hundred feet 

 deep, through solid masses of the very hardest quartzose rock, 

 as is the case in the border district of England and Wales 

 with those diminutive rivers the Teme, the Onny, and the 

 Wye, where they break through the escarpments presented 

 to them ? Those rivers I quote purposely, because it can be 

 shown that where they so break through, there are great dis- 

 locations of the strata from causes which are not at all doubt- 

 ful, but clearly volcanic in their origin, — and the channels of 

 the rivers themselves occupy cracks transverse to the direc- 

 tion of the rocks they traverse. And if we compare the two 

 examples — making allowance, of course, for the great differ- 

 ence in every item between the condition of the old red sand- 

 stone and plastic clay districts, we shall see that on a small 

 scale, the same phenomena were acted over again in the ter- 

 tiary epoch which did such great things at the period when 

 the older secondary and transition rocks were ruptured. 



That these cracks at Studland are regular fissures, and not 

 accidental channels for rain water, is shown by following 

 them to their source, and measuring their direction. That 

 for instance which is marked 6 in fig. 56, opens upon the 

 shore in continuation of the passage through the lofty plastic 

 clay hills behind, and the opening through the chalk at Three- 

 forked Down, by which the road is traversed from Swanage 

 to Studland, and its direction ranges from S.W. by W. and 

 N.E. by E. Just under the signal -house, where the cliff is 

 from 16 to 20 feet high, the hard beds of sand stone are split 

 vertically down, leaving a space of about three feet between 



63 



Fault in the Ravine to the right of the signal-house, Studland. 



the walls ; on the south side the beds dipping to the N.E. at 

 about 24°, exactly agreeing with the dip at the Red Rock, 



