Chalk Strata of Ballard Head. 



465 



700 ft., the consequence must have been, that a crack would 

 be produced in the line of the strain from below ; and the 

 southern portion of the fractured chalk being thus disengaged, 

 it would naturally be moved first diagonally upwards a little, 

 and then, from the very nature of the case, slip backwards 

 under the pressure of lower formations ; then forced up, filling, 

 in its fall backwards, some of the vacant space which, in all 

 probability, was produced by the elevation of the adjacent 

 beds from the green sand to the Portland oolite. 



The pressure still continuing, and the elevatory motion 

 being continued, the undoubted effect must have been, to slip 

 the southern part of the chalk under the fault, the whole 

 range of strata from Tilly Whim to Ballard Down (see 

 jig. 43.) being drawn out like a pack of cards into a length- 

 ened diagonal shape by the double force. The consequence 



47 





■ 



of this would be, that the beds of chalk (horizontal infig. 47.) 

 would first become slightly elevated, and then cracked, as in 



Jig. 48., where the line a b represents the fault ; next, as 

 shown in fig. 49. where the beds are seen, to the south of 

 Vol. I.— No. 9. n.s. m m 



