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of testacea at the higher of these altitudes, it is demonstrable, that 

 when the sea deposited the shells in Moel Tryfane it did not stand 

 at that height above the whole of England, but that the local appear- 

 ances resulted simply from unequal elevation of the sea's bottom. 



All the analogous phenomena in the British Isles seem to lead to 

 the same conclusion. Whilst the modern marine alluvia of the cen- 

 tral coiinties are found to rise towards Snowdon as a great centre of 

 elevation, the banks of gravel with similar shells ascend from the 

 coasts of Lancashire towards the Penine chain in the interior. 

 Again, in the'south-west of England, the most distinct sea-beaches yet 

 noticed, were ascertained to rise very perceptibly from a low level 

 on the south coast of Devon and Cornwall, to heights of 120 feet 

 above the sea in North Devon, where the elevation is more in- 

 tense. The valley of the Severn afforded similar proofs ; the beds 

 of gravel with sea-shells, between Worcester and Gloucester, near 

 its estuary, are slightly elevated above the sea, but in ascending to 

 its source, the same gravel and shells occur at altitudes of 500 to 

 600 feet, until finally they are seen in the lofty cliff's of Moel Try- 

 fane, before alluded to. 



Whilst such may be justly received as absolute pi'oofs (quite 

 as clear as those of M. Bravais) of more intense elevation at 

 some points than at others, the submarine forests along our 

 coasts have been supposed to offer proofs of subsidence. These 

 evidences, however, are not of the same satisfactory nature as 

 those of elevation, for it may in some instances be contended, that 

 the forests in question grew upon low deltas, and have been over- 

 whelmed by irruptions of the sea, which broke down certain banks 

 or natural barriers, that at one period protected them from inunda- 

 tion. But granting these submarine forests on the east coast of 

 England to be really as good proofs of a depression of tlie land as 

 any which exist on the shores of Scania, where a great subsidence 

 has been established, it must also be borne in mind, that the rocky 

 western coast of our island offers equal signs of depression, since 

 Cornwall and Pembrokeshire, and even Cardigan, so near to the 

 point of intense elevation, Snowdon, have each their submerged 

 forests as well as Lincolnshire. Examined, then, as a whole, Eng- 

 land offers many evidences which to me seem conclusive, that within 

 a very recent ])eriod, the land has undergone great and unequal 

 movements, both of elevation and depression, in relation to the level 

 of the sea. Scotland and Ireland present like phasnomena. In the 

 latter country modern marine shells have been found in many localities 

 at various altitudes. Scotland, so rich in superficial accumu- 

 lations, also offers near her shores many testimonies of former sea- 

 bottoms laden with numei'ous shells, but hitherto these remains 

 have only been found at comparatively low altitudes. Another 

 class of detritus, in which, in common with England, she is rich, 

 consists of extensive irregular accumulations of clay, boulders and 

 gravel, usually called " till," and which may be compared with the 

 drift of the tract extending from Bedfordshire and the eastern 

 side of Huntingdonshire, to the coasts of Norfolk, Suffolk and Essex. 



