210 WAVES OF THE SEA 



fore, on account of its enjoying shelter from dis- 

 turbance. I suppose its maintenance to be due 

 to horizontal circulation caused by meeting of two 

 currents at right angles, this repetition of 

 path giving time for the somewhat slow rate of 

 subsidence of sand to take effect. High water at 

 the Bill occurs in the middle of the 9 hours' outset 

 from the West Bay, and less than an hour after- 

 wards occurs the meeting at right angles with the 

 outset on the east side of the Bill. Thus the pre- 

 sumed rotation is set up at the time of greatest 

 wave action on the Chesil Beach, when the outset 

 from the West Bay must be most heavily charged 

 with sediment. 



The outset from the East Bay of Portland pre- 

 sumably contributes sediment to the Shambles 

 when the main tidal current is setting to the east- 

 ward. The tidal current sets westward at the 

 Shambles at about 1 1 hours F. and C. i.e., about 

 the time of low water and at the time of cessa- 

 tion of the outset from West Bay. The outset 

 from the East Bay is then running, and continues 

 to do so for another 5 hours i.e., until 4 hours 

 F. and C. That no shoal corresponding to the 

 Shambles is formed by the west -flowing current 

 on the west side of Portland Bill is to be ascribed 

 largely to the lower water-level and consequent 

 lesser wave action on the shores. 



