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Mackintosh — Geological Notes on Devon. 



are difficulties connected with the marine theory of accumulation, 

 but if we suppose the action of waves, currents, and storms at 

 different tidal levels, and during possible variations of level, arising 

 from oscillations of the land, many of the phenomena can perhaps be 

 explained. Mr. Tylor (Quart. Journ. Geol. Soc, Nov. 1866) seems to be 

 of opinion that the valley was filled with loam up to the level of the 

 cliff above the cavern, to enable the Mollusks to pursue their boring 

 operations, but this cliff is so small that a very slight accumulation 

 of loam beneath it would give a nearly continuous contour to the 

 side of the valley (see Fig. 1). 



Fig. 1. — Diagram of the north entrance to Kent's Cavern. 



L. Loam, x x. Pholas-hotmga. The dotted line represents Asheldon Hill. 



That the cavern was originally excavated or enlarged by the sea 

 is evident from the arched form of the south entrance, and the 

 rounded shape of the recesses and parts of the roof. There are 

 holes (referred to by Mr. Pengelly) on the projecting part of the cliff 

 above the north entrance, and on the roof of the entrance ; and 

 within the arch of the south entrance (Fig. 2) there are somewhat 

 similarly shaped holes, all of which may be slightly weathered 

 PAoZas-borings, though very far from decided specimens. 



Fig. 2. — Diagram of the south entrance to Kent's Cavern. 



L. Loam, x x. Pholan-hoxmgs, Above the loam there is a deposit of Stalagmite covered by a 

 layer of dark-coloured earth. 



On the slope beneath the cavern, if there are not decided Pholas- 

 borings, there are convincing wave-marks on the projecting rocks. 

 On Asheldon (the hill nearly opposite Kent's Hill), I have seen 

 fresh-looking PAoZas-borings at a lower level than the cavern. These 

 facts furnish a strong presumption, in the absence of evidence to the 

 contrary, that no flow of water capable of abrading rocks, has been 

 in the valley of Kent's Cavern since it was last under the dominion 

 of the sea. 



