276 JOURNAL OF THE PLYMOUTH INSTITUTION. 
familiar upheaval and eddy as at Devil’s Point. It is obvious, 
from the structure of this basin in solid rock, that it could never 
have been excavated in this way, and to this extent, by the ordinary 
attrition due to running water. Some other explanation must be 
found. 
On the Devonshire and Cornish coasts the main outlets of the 
drainage have a striking similarity. Falmouth, Fowey, Plymouth, 
Salcombe, and Dartmouth have, when compared, a significant 
resemblance; Falmouth, Plymouth, and Salcombe especially so. 
In all we have the contracted exit to the sea guarded by rocky 
cliffs, and in the rear a rounded gently undulating expanse of 
country discharging its drainage at this exit. It would seem then, 
that these harbours all owe their present configuration to the same 
agency; a fact which renders the explanation of these excavations 
in rock by direct volcanic or similar action somewhat doubtful. 
Take for instance the depression at Plymouth; this has all the 
peculiarities of a true ‘‘rock basin,” for the narrower and deeper 
portions occur just in those places where the erosive power of 
ice would have been greatest, and as the valley opens out the basin 
shallows. Such excavations on an extensive scale are of frequent 
occurrence in Scotland, where the whole of the western coast, both 
above and below the present sea level, owes its configuration en- 
tirely to the erosive power of glacier ice.* Whether similar 
depressions on the south coast of England are the work of ice or 
not is a question which has yet to be decisively settled. Compara- 
tively little local evidence has so far been obtained on this important 
subject. 
Evidences of great change in level are abundant on the south 
coast. Raised beaches and submerged forests are of frequent 
occurrence, proving that within a comparatively recent date, with 
the same general contour of coast line, and disposition of land and 
drainage, there were thirty or more feet of variation in level, above 
and below the present mean sea mark. 
The silting-up of tidal flats, either naturally or artificially, has 
* See Chart in ‘‘ Geikie’s Great Ice Age.” 
+ ‘Evidence of Glacial Action in South Devon,’ by E. Vivian, Trans. 
Dev. Assoc., p. 357, vol. ii. ‘Is there Evidence of Glacial Action in the 
Valleys of Dawlish and Ashcombe, South Devon?”’ by G. Pycroft, Ibid, 
p- 75, vol. v. ‘Notes on Boulders and Scratched Stones in South Devon,” 
by W. Pengelly. Parti., Idid, p. 154, vol. vii.; part ii., p. 177, vol. ix. 
