Mr Smith on the Changes of the Level of the Sea, 387 



naturally stir up the clay so as to fill dead shells. Those found 

 in this locality do not bear marks of violent transportation, and 

 the distance from the sea is so great that it is difficult to sup- 

 pose that such fragile shells as the Mytilus edulis and Tellina 

 approxirna could have been borne along uninjured by diluvial 

 action. I am, therefore, inclined to consider, that the shells 

 found at Airdrie belong to the alluvial beds, and have been 

 confirmed in this opinion by having had some specimens of 

 the Tellina appronima, a species which has only been found in 

 this deposit, sent to me from the same locality. 



Mr Prestwich* also found, at the height of 350 feet, in beds 

 of sand, gravel, and clay, at Gamrie, near Banff, the following 

 recent shells : Astarte Scotica, Tellina tenuis, Buccinum unda- 

 turn, Natica glaucina, Fusiis ttirricola, Deiitalmm dentalis. 

 They were extremely friable, but perfectly uninjured. 



The promontory of Brayhead, in the county of Wicklow, is 

 formed by a cliff of alluvial strata of coarse gravel and sand, 

 containing sea shells ; it is at least two hundred feet high, and 

 the hill of which it is a part, and which is evidently composed 

 of the same beds, is perhaps a hundred feet higher. Here, 

 therefore, this deposit reaches to the height of three hundred 

 feet. At Howth, on the north side of Dublin Bay, are similar 

 cliffs, at the height of about a hundred feet, also containing 

 shells and other marine exuviae. 



In the Isle of Sheppey,f recent shells have been found in 

 a bed 140 feet above the present level. In Norfolk,} and in 

 5rorkshire,|| they have been found at the height of a hundred 

 feet Near Berwick, Mr Milne § observed a tract of table-land 

 at the height of a hundred feet above the level of the sea. It 

 consists of vertical strata, which have all had their edges worn 

 down to a level plain, just as would have been the case if the 

 rocks had been exposed to the action of marine currents inces- 

 santly sweeping over their edges. When the tide is far out, 

 exactly the same appearance is presented by the vertical rocks 

 which form the bottom of the shore for a considerable distance 

 out from the existing cliffs, and were there to be an elevation 



* Proceedings Geol. Soc. May 3. 1837. t lb. voL i. p. 410. 



t Phil. Mag. Jan. 183G, p. 30. || PhiUip's Geology, p. 198. 



§ Fourth Report Brit. Assoc, p. 638. 



