SPECIAL GEOLOGY. 



395 



The Purbeck beds, and their 

 overlying sands, are well seen 

 in the coast sections of the 

 south-western shores of the 

 Isle of Purbeck. The relative 

 position of these beds is exhi- 

 bited in fig. 275. 



GrEOGBAPHICAL DlSTBIBU- 



TION. The wealden extends 

 from Horsham to Hastings, 

 where it dips beneath the sea, 

 forms the bed of the English 

 Channel, and re-appears in the 

 valley of Braye, in the pro- 

 vince of the Boulonnais ; thus 

 occupying an area of 200 miles 

 from west to east, and 220 

 from north-west to south-east, 

 the total thickness being about 

 2,000 feet. Strata resembling 

 the weald clay and Hastings 

 sand have been discovered by 

 M. Eoemer, in Germany, 

 where they occur near Helm- 

 sted, and extend westward 

 from Hanover, by Minden, to 

 Iburg and Rheine, near Mini- 

 ster, in "Westphalia, abounding 

 in seams of good coal, from one 

 to three feet thick. Deposits 

 of like character occur in the 

 Isle of Bornholm ; and, with 

 the progress of geological in- 

 vestigation, it is probable that 

 other instances will be disco- 

 vered, since the land which 

 gave rise to the river of the 

 weald was, doubtless, drained 

 by others flowing in different 

 directions. 



J ! 



