THE GEOLOGY OF THE ENGLISH CHANNEL. 175 



moderately rapid, the sli ore-line would never have presented any con- 

 siderable height of cliff. Fringing the cliff in all bays and many 

 creeks would be beaches of sand and shingle derived chieHy from the 

 local rocks. Beyond the beach, where soft strata existed would be 

 tidal plains of marine erosion, such level surfaces as now exist between 

 tide-marks in Torbay. The constant advance of the sea, the constant 

 depression of the land, would ever carry forward the line of shore, the 

 sea-cliff" for the time being existent, and the beach would follow ; its 

 material would always be largely derived from the actual cliff, but in 

 part consist of older material driven forward by the waves. The 

 rocky plain would sink beneath the sea, and be left as a rather uniform 

 surface of slight gradient seaward. Little or no beach would be left 

 behind, and the older constituents of the beaches, those derived from 

 the outer previous shore-lines, would never long persist, the constant 

 wear reducing and destroying them. 



Boulders from harder rocks would not be driven on in the 

 same manner as pebbles and shingle, but would remain near their 

 points of origin. Until, however, some considerable depth of water 

 flowed over them, sucli boulders would still be liable to wear from ex- 

 ceptional wave action ; and, further, we may consider that, especially 

 with the granitoid rocks, submarine weathering must produce, but in a 

 greatly less degree, the familiar effects of subaerial exposure. The 

 chief and important difference would arise from the more uniform 

 temperature of the sea. 



There is reason to believe that the first inlet of the sea was some- 

 what long and narrow, a comparatively sheltered area, where wave 

 action would be slight. That large and relatively unworn stones 

 might be left here would be no occasion for surprise. And as the land 

 sank and the Channel widened, this first-formed portion of its bed 

 would still receive some shelter, until it was covered with water too 

 deep to permit destructive wave-action. Extending the argument, 

 there seems here a reasonable explanation of the general increase in 

 the size of the dredged stony material outward into the Channel. 

 Other causes may have co-operated. That wave action beyond the 

 forty-fathom line has little or no destructive effect upon the pebbles 

 at present, may be judged by the existence of pieces of yellow chalk 

 and of Lias limestone bored and riddled through and through and yet 

 in pebble form. 



But in a narrow sea, while the wave action would be slight the tidal 

 currents would be swift, and sand would not readily deposit ; hence the 

 fact that these stones were not buried beneath finer deposits derived 

 from the shores. 



