A RETROSPECT. 193 
We see within our own time, devastations and 
ravages of considerable amount committed on the 
occurrence of even minor floods originating in all 
likelihood merely in the force of a sea wind exerted 
during the menacing elevation of a spring tide. Al- 
together indeed, our exposed position relatively to 
the sea causes disintegration to be conducted on our 
cliffs with great rapidity, and there can be no doubt, 
the destruction would be still greater if it did not 
fortunately happen that our slate dips so generally 
towards the channel, and thereby lessens the bat- 
tering influence of the waves. 
Modern authors with great propriety agree in 
attributing considerable geological effects to the 
discontinuanee of river courses, the filling up of 
estuaries, and still more, to the general subsidence 
of the ocean in the northern portions of the world ; 
they have traced the results of these proceedings in 
the occurrence of marie matter inland, and in the 
gain of considerable tracts of land, especially of 
course, where the country is generally flat. I pur- 
pose now to examine how far these natural causes 
have extended themselves into operation in this 
immediate neighbourhood. At the time when the 
sea stood so far out as to admit of forests growing 
where now is deep water, the rivers were naturally 
continued outwards considerably beyond their pre- 
sent terminations ; that spot now occupied by the 
Lara or estuary of the Plym may therefore have 
originally been the site of a sylvan district, with 
the river or its yet parent branches passing towards 
its ultimate abode, and flowing probably over the 
very surface of the slate rock which it has been - 
found constitutes the substratum of this river bed 
ata great depth. On the rise of the sea in the 
manner which I have recorded, these woods would 
be overwhelmed, and deposited amid the shingle 
and debris naturally conveyed there by the ocean 
Q 2 
