1'26 Proceedings of the Royal Physical Society. 



driven from Exmouth to Bridport, and by the former they are 

 carried along the bank itself towards Portland, where their 

 further progress is arrested by the counter-wave forces that 

 then take action under the influence of the south-south-west 

 winds prevailing at other periods. 



^th, Much argument has taken place regarding the dis- 

 tribution of the pebbles on the bank, to account for the pre- 

 sence of the larger stones on the crest, and at the south-east 

 or larger end, and the smaller at the north-west end, and 

 at the base, and views on this point are to be found fully 

 stated in the communications previously quoted. 



^th, It may, however, be mentioned that the storm waves, 

 which are the builders of the embankment, have a tendency 

 to urge upwards a mass of pebbles by their forward surge, 

 containing the larger ones foremost, and the smaller ones 

 behind ; and that the backwash leaves them stranded in the 

 order of its inability to drag them back. 



10th, This may be due to the velocity of the surge being 

 greatest on its margins to the land side when rising, and 

 least there when beginning to fall back again down the slope, 

 where it is further spent by sinking down between the stones 

 into the interior of the bank. 



11th, An explanation of the transportation of the larger 

 pebbles from the smaller north-west end of the bank to the 

 larger south-east end, may be offered by supposing that the 

 storm waves, when surging obliquely against the slopes in 

 west-south-west winds, drive the pebbles up the bank ob- 

 liquely, and leave them there to be projected still further 

 obliquely by the next following surges, as they rose liigher 

 and overtook them towards the eastward. 



12th, Why does the Chessil Bank lie in a north-west and 

 south-east direction ? The reply may be that the south-west 

 storm waves, which surge in parallel lines to its length, over- 

 come by their superior force the migratory actions of the 

 west-south-west and south-south-west wind waves, exerted at 

 other times, and drive the stones then left behind perpen- 

 dicularly up the bank to its crest, which the other weaker 

 wind waves are unable to reach afterwards. 



13^7^ The seaward face of the bank is terraced by the 



