116 Mr. P. I. Martin's Observations on the Anticlinal Line 



in the stony beds, and an eroded thinned-off surface in the 

 clays. Tliese phaenomena are to be traced down to the 

 lowest beds of the wealden, in the Weald Valley, or in the 

 Wiltshire Vales, and down to the mountain limestone in the 

 Boulonnois*. 



In the study of the whole, or of a part of this anticlinal line, 

 the naturalist who takes for his guide the image thus pre- 

 sented to his mind, will find all its variety of surface satisfac- 

 torily accounted for, and all its parts in harmony with each 

 other. Evidence of elevation and subsidence, fracture, watery 

 erosion, prominence or depression, all answering to the com- 

 pound actions of convulsion and watery flood. 



In carrying on this investigation a little further, and taking 

 it for granted that all the formations above it have rested 

 where we now find the wealden only, — a curious and almost 

 unexpected result displays itself, if we picture the restoration 

 of the lost materials. Crowboro', in Sussex, the highest geo- 

 graphical point of the lowest geological bed, rises 800 feet 



above the level of the sea 800 



If to this we add for the remainder of the wealden above 



it, at a moderate computation 600 



For the glauconite 500 



For the chalk — Mr. Conybeare thinks that the thick- 

 ness cannot be fairly judged by the vertical beds of the 

 Isle of Wight, where it is 1300 feet; but it may at 



least be computed at 800 



Plastic clay 700 



London clay 400 



Bagshot sand, the Headon Hill, or whatever other 

 strata are known to lie on the London clay , . . 200 



Feet 4000 



Almost double the thickness here stated is given to the 

 plastic clay by Mr. Websterf; but I have followed Mr. Co- 

 nybeare, although I think that he has over-rated the expan- 

 sion which he supposes to have occurred to this as well 

 as to the chalk stratum in the vertical beds of the Isle of 

 Wight. The extent of the superficies of the upper chalk of 



the beds afterwards fractured and furrowed into valleys and mountain 

 ranges. Similar, though less regular, lines may be observed in the sides of 

 many hills composed of rocks of regular stratification, and always on 

 eroded superficies of unequal densities. 



* Proceedings of Geological Society, 1827; and Conybeare and Phillips's 

 " Outlines,'' &c. 



f Gcol. Trans, vol. ii. 



the 



