434 Bristow and Whitaker — On the Chesil Bank. 



might produce the present appearances ; for though, the sea would 

 have attacked the land when the relative levels were different, the 

 form of the bay, and the projection of the Isle of Portland, would 

 soon cause a beach to be formed, which would rise as the land sunk, 

 so that finally no traces of a back cliff could be observed. Under 

 this hypothesis Portland would not have formed an island, but 

 merely the projecting point of a bay, which, with its exposure, 

 would soon have accumulated the beach required. It may be re- 

 marked that this supposed gradual sinking of the land is in accord- 

 ance with appearances more westward on the same coast, where the 

 facts presented seem to require this explanation." ^ 



Sir C. Lyell is the author of another theory. He says ; " The for- 

 mation of this bar may probably be ascribed, like that of Hurst 

 Castle, to a meeting of tides, or to a great eddy between the penin- 

 sula and the land We may expect the slightest impediment 



in the course of that tidal wave, which is sweeping away annually 

 large tracts of our coast, to give rise to banks of sand and shingle 

 many miles in length, if the transported materials be intercepted in 

 their passage,"^ In later editions this is repeated, with the addition 

 " or to a submarine shoal or reef between the peninsula and the 

 land," in which form it is supported by Mr. Coode, according to 

 whom " the isolation of the bank is due to the existence of a level, 

 or nearly level, bench of clay, upon which the shingle is thrown 

 and rests, as upon a shelf." ^ In Sir C. Lyell's last work the theory 

 is thus stated : " That part of the bar which attaches Portland to the 

 mainland rests on Kimmeridge Clay, which is sometimes exposed to 

 view during storms. The clay may have formed a shoal, and the 

 set of the tides in the narrow channel may have arrested the course 

 of the pebbles, which are always coming from the west," * 



Colonel G. Greenwood, however, accounts for the occurrence of 

 the Chesil bank on the supposition that, in consequence of a rise of 

 the land, the sea would have a shallower shore, against which it 

 could throw up the pebbles. His words are as follows : " Eaised 

 beaches exist along our south coast, and I think that it is the 

 shallows caused by the rising of the land that has [have] allowed 

 the accumulation of double beaches between Giens [East of Toulon] 

 and the land, as well as between Portland and the land (Chesil 



beach and Smallmouth sands) Kature has no sooner divided 



the island from the continent than, by hoisting Tip the land, she sets 

 the same workman, the sea, whom she first employed to sever them 

 [it] from the land to join them [it] to the land again." ^ 



These three theories may be described as the sinking theory ; the 

 standing still theory (by implication, as its advocates say nothing of 

 rise or fall), and the rising theory; each of those conditions of the 



1 Geological Manual, Ed. 3, 8vo. Lond., 1833, p. 80. The theory is repeated in 

 the author's later work, the Geological Observer, 8vo. Lond. (1851), p. 65, aud Ed, 

 2 (1853), p. 56. 



* Principles of Geology, vol. i. p. 281 (1830), 1st edition. 

 3 Proc. Inst. Civ. Eng., vol. xii. p. 542 (1853). 



* Principles of Geology, Ed. 10, vol. i. p. 534 (1867). 



* Eain and Rivers, Ed. 2, 8vo. Lond. (1866), pp. 119, 132. 



