OF THE LEVEL OF THE SEA. 57 



not invalidate the conclusion, that the changes in the level 

 are posterior to the deposition of the till, they only prove 

 that it has not swept away the whole of the pre-existing al- 

 luvia. I have observed the marine beds resting on Till near 

 Glasgow, and in the excavations of the railway from Edin- 

 burgh to Newhaven. Mr Thomson has observed it in 

 Dumbartonshire.* At Johnstone, near Paisley, in digging 

 a well, a marine deposit, containing the bones of fishes and 

 sea-fowl, the claws of crabs, sea- weed, and shells, was found 

 to rest upon a bed of it, upwards of 70 feet in thickness. 

 Mr Robberds-f* and Mr Rose J have observed the same or- 

 der of position in the county of Norfolk. 



We can, therefore, have no hesitation in considering that 

 in these localities changes of level have occurred posterior 

 to the deposition of the diluvial covering, although it is not 

 improbable that in some parts of the British islands it may 

 have been lodged on the surface subsequent to the period 

 when the sea had become stationary at its present level. I 

 am inclined to think that this has been the case on the west 

 coast of Ireland ; in the counties of Clare and Kerry I ob- 

 served no stratified beds above the diluvium, and, on the 

 shores of the Shannon which divides them, no terraces ex- 

 cept those forming at present. These facts, however, seem 

 rather to prove different periods of diluvial agency than of 

 elevation and depression. 



The changes of level must have taken place anterior to 

 the historic period, which in this country dates from the in- 

 vasion of the Romans. Diodorus Siculus,§ who wrote du- 

 ring the reign of Augustus, describes St Michael's Mount 



* Records of General Science, i. 132. 



t Phil. Mag. Oct. 1827, p. 281. J lb. Jan. 1836, p. 34. 



§ Diod. Sic. Book v. Quoted in Thomson's Outlines of Mineralogy 

 and Geology, vol. ii. p. 45. 



