198 WAVES OF THE SEA 



north-west to, say, south-by-west, and it is a pocket 

 into which, if a large pebble be driven, it cannot 

 escape in either direction. 



Finally, we must not omit to notice the co- 

 operation of the tides with the eastward drift along 

 this beach. High water on days of full and new 

 moon occurs at about 5^ hours at the Bill of Port- 

 land. But there is a strong outsetting current from 

 the West Bay for 9 hours out of every 12, viz., 

 from 2 hours to 1 1 hours on the days of full and 

 new moon. This comprises all the time when the 

 water is above mean sea-level. Thus, even such 

 waves as do run westward along the beach 

 ( especially near Chesilton ) either have the tidal 

 current against them or else are only beating 

 against the lower part of the beach, where much 

 of the shingle is out of their reach. 



Before leaving the interesting subject of the 

 arrangement of beach shingle, I will give some 

 particulars of my observations between Lyme and 

 Bridport Harbour. Looking at the map, and at 

 a map of the South Coast of England, we see that 

 Lyme Bay is the largest bay on that coast, and 

 that the sudden change in direction of the coast 

 so as to face the south-west occurs, not at Brid- 

 port Harbour, but at Charmouth. It occurred to 

 me, therefore, that Bridport Harbour was not the 



