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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 19, 



the smaller valley of Woolhope. The latter has been described by 

 Sir R. Murchison, and more recently by Mr. Phillips*. It is 4^ 

 miles in diameter, and resembles in size as well as in some of its 

 leading features the Caldera of Palma, the beds, in the boundary 

 cliifs encircling the excavated space, dipping in all directions outwards, 

 and the cliffs for that reason retaining more easily their steepness or 

 verticality. 



3rdly. If the crater of a submarine volcano be upraised and begin 

 to emerge, the sea will still flow into it on its lowest side, and the 

 circular basin will then be filled and emptied alternately by the flux 

 and reflux of the tide, or by the rise of water blown into the opening 

 by prevailing winds, and then falling again as soon as this force ceases 

 to act, by which means a passage will be kept open, the crater being 

 scoured out like estuaries which have narrow entrances. On the 

 efiicacy of this last mode of aqueous erosion I must particularly insist, 

 as it aids us more than any other in comprehending the theory of denu- 

 dation-craters. The Basin of Mines in the Bay of Fundy illustrates 

 the manner in which a large bay, communicating with the ocean by 

 a narrow strait, may be filled and half-emptied every tide, so that 

 the waves and currents may sweep out in the course of centuries a 

 vast volume of mud and sand, and produce on all sides of the bay 

 long ranges of cliffs annually undermined, several hundred feet per- 

 pendicular, some composed of soft red marl, others of hard quartzose 

 grit, and others of columnar basalt. The Bay of Fundy it is true 

 would not present, if it were upraised and laid dry, so circular a hol- 

 low as the so-called crater of elevation, but there are numerous coves 

 on a part of the coast of Dorsetshire which are as perfectly circular, 

 if not more so than the Gulf of Santorin or the Caldera of Palma, 

 and in which the single breach effected by the sea on one side is not 

 larger in proportion to the entire girdle of encircling cliffs. These 

 cliffs moreover, which every geologist attributes exclusively to the 

 denuding action of the sea, are precipitous, and most lofty at the 

 head of the bay or farthest from the entrance, where they consist of 

 inclined strata of chalk. Lulworth Cove, which is 1300 feet across, 

 is the most perfect example (see fig. 3). In this case the hardness of 



Fig. 3. 

 Coast of Dorsetshire. 





Lulworth Cove 



* Murchison, Silurian System, Part I. p. 428, and J. Phillips, Mem. of Geol. 

 Survey, vol. ii. p. 167. 



