existing Physical Causes during stated Periods of Time. 31 
have been brought from the north, in which direction there are 
recorded instances of great destruction of land by storms during 
the last 300 years. 'The aspect, however, of much of the coast- 
line appears as if it had remained unaltered for a very long period, 
except in the manner Mr. R. A. C. Austen* alludes to when he 
remarks, “that although the sea for months together, and in 
places even for whole years, may not acquire any fresh spoil, yet 
there are few hours when its waters are unemployed in fashion- 
ing and abraiding the materials already acquired.” In considering 
the effect upon the sea-level caused by sand, mud, and pebbles 
washed in by the breakers, it is only necessary to regard those 
materials that may be brought in from cliffs above high-water 
mark; for the movement of sand and mud below high-water 
mark can produce no effect upon the sea-level, because the ab- 
straction of these materials from one part of the shore is exactly 
balanced by their addition to some other part. For instance, 
some of the flint-pebbles which have contributed to the recent 
deposit at Landguard Point have been brought along shore a great 
distance from their original position on the cliff. These flints 
formed an addition to the sea-bed, and tended to raise its general 
level by displacing an amount of water equal to their bulk the 
moment they fell on the shore below high-water mark ; and it is 
quite cleat their subsequent movements, either beneath the wave 
ot on the beach, could produce no further effect upon the sea- 
level, the spaces they occupied on one part of the coast being bal- 
anced by the vacancy left at some other. It is also evident that 
the beach at Languard Point will go on extending so long as the 
fresh supplies of shingle and sand from the north exceed the. re- 
movals southward. 
Figs. 6, 7—Sections showing the Increase of Landguard Point between 1804 and 1844 
Beach end in 1804. 


Lise: YH de Lis 
a. a, Low-water level of ordinary springs. 
In the same manner the continued supplies of pebbles from the 
Westward enables the Chesil Bank to preserve its position. As 
* Austen, Quart. Jour, Geol. Soc, vol. vi. p. 71-73 ; and De la Beche, Geol. Obser- 
ver, 1851, p. 65, 
