AND OTHER WATER WAVES 203 



and the height of the beach greater. The increase 

 in the size of the shingle, however, is for most of the 

 way a very gradual process, becoming rapid only 

 when near the shelter of the Portland promontory. 



Thus I found that wherever there was shelter 

 from the east there was a pocket filled by a high 

 beach composed of large shingle. The arrange- 

 ment is therefore due to the normal sorting action 

 by the waves, in which the local tides happen to 

 assist. 



I have shown why the large stones collect at 

 Chesilton, but I must add a word on the probable 

 mode of removal from the steep shore in that 

 agitated corner, of the large quantity of small 

 angular fragments which are mixed up with the 

 boulders between the end of the true Chesil Beach 

 and Blacknor Point. There is little trace of them on 

 the beach at Chesilton, and the bottom off there is a 

 good holding anchorage of clay. A strong under- 

 tow setting towards Portland is a matter of local 

 knowledge, and Captain King's " Pilot's Handbook 

 for the English Channel " furnishes detailed in- 

 formation on the subject of the outsetting current. 

 It runs for 9 hours out of every 12 (so long does 

 it take to relieve by a narrow stream the water from 

 the broad bay which has piled up in the Chesilton 

 corner), and closely skirts the rocky shore, gradu- 



