234 



AN ANCIENT PORTLAND INTERMENT. 



Purbecks were once spread over the island ; blocks of it occur in 

 several places. The loam above Chesilton contains angular frag- 

 ments of it, and south of the Verne is a drift bed of great 

 antiquity, full of angular local debris of both Purbeck and Portland 

 stone, together with a considerable number of Sarsen stones from 

 the Lower Tertiaries. The anticlinal of the Weymouth valley 

 shows the extent of the denudation to which the district has been 

 subject, and again the raised beach at the " Bill," 40 feet above 

 the sea-level, and the remarkable deposit of sand and gravel at a 

 still lower level further westward, show the elevating forces that 

 have been at work during the Quaternary Period and since. The 



<? R o u 



LEVEL 



A R T-H 



PURBECK STONE 



H 



,0irt Be.& 



Gcd 



SECTION 



remains rested on the top of the Whit-bed at its junction with 

 the Roach bed, through which the fissure passed. A foot and 

 a-half above them there was a layer of stalagmite, an inch and 

 a-half thick. A few feet from the fissure there was a large 

 cavernous space filled with blocks of stone from the superincumbent 

 Roach-bed, which I consider to be the continuation of the fissure, 

 extending probably through the succeeding strata down to the 

 Portland clay. One of my companions descended into this fissure, 



