Chalk Strata of Ballard Head. 



417 



cles, and finally tore away the solid masses themselves, and 

 hurled them into the sea, was occasioned by the same general 

 causes as have produced the results before alluded to, on so 

 large a scale, and over so large a space. I shall have an 

 opportunity, further on, of showing that the same agencies 

 appear to have been at work in modifying the present surface 

 of the highly varied and deeply excavated deposits of the 

 plastic clay series in the vicinity of Poole and Christchurch. 



In illustrating the particular phenomena presented by the 

 section of the vertical chalk at Ballard Head, near Swanwich, 

 it will be necessary to represent, by woodcuts, the general 

 features of the locality. On approaching from the sea the 

 eastern termination of Purbeck, the coast appears as repre- 

 sented in J%s. 35. and 36.; the latter being merely a con- 

 tinuation of the former. 



In Jig. 35. the overhanging, dark, curved strata and 

 breccia of Purbeck stone at Durlstone Head, the highly 



Swanwich Bay. 



1, Durlstone Head. 2, Peveril Point. 3, Swanwich town. 4, Quarries in the Purbeck 



strata. 5, Top of St. Aldhelm's Head. 6, Inclined cliff's of Hastings sand. 7, Vertical 

 strata in cliffs of hard chalk, Ballard Head. 



inclined red cliffs of Hastings sand in Swanwich Bay, and 

 the commencement of the chalk cliffs ranging from Ballard 

 Head, are sufficiently represented to show the order of suc- 

 cession and inclination of the separate formations. Fig. 36. 



Chalk Cliffs from Ballard Head to Old Harry. 

 7, Junction of vertical and curved strata. 8, Old Harry Point. 



represents the chalk from Ballard Head to Old Harry Point, 

 forming the southern horn of Studland Bay. 



It will be seen that the older formations rise from under 

 each other at an angle continually increasing, till it becomes 

 90° under Ballard Down ; and that at Ballard Head the 

 vertical strata are in contact with curved strata; which latter 

 gradually approach towards a horizontal direction, as repre- 



