118 LEWIS G. WESTGATE 
bottoms of stream-beds shows that abrasion has not been a deter- 
mining element in valley-deepening, and that the stream is a trans- 
porting and not an abrading agent, removing materials dislodged from 
its bed or swept into it from its valley sides. 
WAVE-EROSION 
As in river-erosion, so in wave-erosion, abrasion, or the wear by 
material thrown against the base of the cliff, has been generally 
emphasized in the texts. Chamberlin and Salisbury make corrasion 
by the impact of detritus an important element in wave-erosion on 
hard rocks, at the same time emphasizing the co-operation of weather- 
ing along joint planes. Geikie? says: ‘‘The waves make use of 
loose detritus within their reach to break down cliffs exposed to 
their fury. Probably 
by ‘fare the largest 
amount of erosion 
is thus accom- 
plished.’ Le Conte’ 
says that ‘‘fragments 
hurled against the 
shore are the princi- 
pal agent of wave- 
Erosion: 2 aD uiresit 
abrasion has been 
the determining fac- 
tor in wave-cutting, 
the shore in the verti- 
cal zone of breakers 
should bear evidence of this by its rounded and worn character. 
The only chance which the writer had to study rock shores with 
this consideration in mind was at Newport. In the hard con- 
glomerate and sandstone at Easton’s Point (see Fig. 3), on the 
south side of the island, no evidence of abrasion was found. ‘To be 
sure, in some protected pockets, into which gravel had been swept 
Fic. 3.—Shore on the east side of Easton’s Point, 
Newport, R. I. 
t Chamberlin and Salisbury, Geology, Vol. I, pp. 327-29. 
2 Geikie, Text-Book of Geology, Vol. I, p. 569. . 
3 Le Conte, Elements of Geology, 5th ed., p. 34. 
es = 
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