THE RIDGWAY FAULT. 57 



George III. of later date, the escarpments rising like a wall from 

 the lowlands of the vales dotted with white pits seen as landmarks 

 so easily from a distance ; these all owe their origin to the chalk, 

 whilst a glance at the geological map of England discloses the fact 

 that here, in the western portion of the county, the various ridges 

 of the chalk forming the Xorth Downs, the South Downs, and the 

 backbone of the Isle of Wight, and the Purbeck Hills converge into 

 a parent nucleus. Across the bay in the grand cliff of Whitenose, 

 too, we see the southernmost point in England, where the white 

 chalk stands as a cliff from the water's edge. Xearer the western 

 portion of the county, again, we are brought in contact with other 

 interesting problems in connection with the chalk, for the lower 

 beds have been gradually becoming thinner in the passage from the 

 eastern portion of the basin westwards, until at Bere Head the 

 upper chalk is found resting on the Upper Greensand, and the 

 lower chalk, from Mr. Whittaker's observations, is represented by 

 the Bere rock. 



In the western and north-western portions of the county the 

 character, of, not the chalk itself it is true, but of beds closely 

 beneath the chalk, becomes very interesting. The Chloritic Marl 

 becomes extremely fossiliferous in the neighbourhood of Maiden 

 Bradley, Chardstock, and Minterne. Xear Chard the curious 

 tabular flints occur in the Greensand at the base of the chalk, 

 unlike anything of a silicious nature in this neighbourhood, of 

 which we saw some excellent examples at our meeting in that 

 district in July last year, and lastly we cannot omit from our 

 survey the curious and interesting character which the Greensand 

 assumes still further west at Blackdown. On such grounds as these 

 the chalk formation, and the beds immediately connected with it 

 below, become of special interest to the Dorsetshire naturalist. 

 Still, however, it is an undoubted fact that we have no account of 

 the Dorsetshire chalk as a whole ; the published memoirs of the 

 Geological Survey do not embrace our own county, and reports 

 which occur from time to time in the Quarterly Journal of the 

 Geological Society, and elsewhere, deal with special points only. 



