386 Mr Smith on the Changes of the Level of the Sea. 



In Ireland, I have seen them on the east, north, and west 

 coasts. I am informed by Mr Griffiths, that he has observed 

 them in Cork and Waterford, and Captain Portlock has recent- 

 ly found them in stratified beds at an elevation of 400 feet. 

 Proofs of such changes have also been observed in the Channel 

 Islands and on the opposite shores of the Continent, all proba- 

 bly referable to the same geological epoch. 



These marine beds have been discovered at every elevation, 

 from that of the present level of the sea to a height of at least 

 400 feet above it ; and in the solitary instance of Moel Try- 

 fane shells have been found at the height of 1400 feet; but as 

 the cause of their occurrence in that situation is doubtful, we 

 may conclude that the highest elevation at which proofs of 

 such recent changes have been hitherto discovered is limited to 

 400 feet. 



At this height Mr Gilbertson found sea-shells in stratified 

 beds of gravel and sand near Preston in Lancashire. Mr Mur- 

 chison,"* who visited this locality, observed " similar pheno- 

 mena over a very considerable tract of country occupying the 

 ancient estuary of the Ribble. Sands, marls, and gravels, occa- 

 sionally forming terraces, are spread over this great area, some- 

 times in finely laminated beds, but for the most part loosely ag- 

 gregated, and bearing a great resemblance to the arrangement 

 of the same materials now in the act of formation on the adjoin- 

 ing shores. Many of the shells found in these beds far inland, 

 and at heights extending to 300 feet above the sea, are perfectly 

 identical with existing species.*" Mr Murchison justly infers, 

 that such appearances must be ascribed to actual elevation ra- 

 ther than to the action of diluvial currents. Sea-shells were 

 found by Mr John Craig, mineral surveyor, at Airdrie about ten 

 miles to the east of Glasgow, at the height of about 350 feet ; 

 they were found between a mass of blue till and a bed of yellow 

 stratified clay, which rested upon it. Mr Craig was inclined to 

 suppose they belonged to the till, the shells having been filled 

 with blue clay ; but I have observed th& same thing in shells 

 which certainly belonged to the stratified deposit, and it is easily 

 accounted for. The action of the sea upon such a bottom would 



* Address to Geological Society, Feb. 1832. 



