STUDLAND. 



393 



truding and bulging central part of the buttress can resist the 

 elements long after the sea shall have a little further under- 

 mined the base. The changes, therefore, in the outline of 

 these cliffs, cannot be exactly uniform, but must be produced 

 by different measures of decay ; and it also follows, that that 

 decay must be of a more rapid character than if there were no 

 assistance offered by these natural rents. 



These vertical fissures are curious also in a more important 

 geological sense. It is observed that they occur only where 

 the chalk strata are horizontal, or nearly so ; and that the fis- 

 sures which traverse the vertical beds are at right angles, or 

 nearly perpendicular, to the direction of the fault which oc- 

 curs at Ballard Head, (vol. i. p. 467). Now this, upon the 

 supposition I have advanced before, should be exactly the 

 case; and, therefore, these vertical rents are nothing but 

 joints, traversing the whole solid body of chalk, consequent 

 upon the strain of elevation. There are two other evidences 

 of this fact. At the approach of the chalk to the plastic clay, 

 at the bottom of Studland Bay, represented at I and J in the 

 diagram (fig, 47), which gives the plan of the cliffs from the 



Plan of the chalk cliffs from point E to the plastic clay cliffs, Studland Bay. 

 At I and J faults numerous. At L, a spring rises from the beach, 11 paces from the cliffs 



At N and O, conglomerate. 1 , Plastic clay. 2, Boat-house. 



The numbers represent the distance in paces. 



point E in the map, and in figs. 45 and 46 looking westward, 

 faults are very numerous ; and in several cases there is the 

 plainest proof that the masses have been ground against each 

 other, as the surface of the chalk is sometimes ground smooth, 

 and is shining, as if covered with slickensides ; in other in- 

 stances, the surface at the fault is covered with a thin coating 

 of yellowish iron, which is striated by scratches exactly after 

 the manner of the surfaces of faults in the older rocks. The 

 flints in the vicinity of these faults are all fractured in situ, 



