284 Scientific Proceedings, Royal Dublin Society. 



be right, and that under certain circumstances sand and shingle 

 may be travelling across the same line in contrary directions. 

 It may be observed here that, in the shingle-bank thrown up at 

 Oddicombe by a severe gale from the southward and eastward, on 

 Sej)tember 1st, 1883, the shingle gradually decreased in size from 

 N.N.E. to S.S.W. In this case there was no doubt whatever 

 that the shingle was larger to leeward than to windward. 



Lyme Bay, with its numerous minor indentations, between 

 Portland and the Start, has presented many knotty problems for 

 solution concerning the travel of beach-material. Of these there 

 may be specially noted the reversed directions of the Teignmouth 

 and Exmouth sand-spits, though but a few miles apart, the assort- 

 ment of shingle in gradually decreasing or increasing sizes, as the 

 case may be, and the exceptional height of the Ohesil Bank above 

 mean-tide level. It seems likely that the problem presented by 

 any beach in Lyme Bay or elsewhere will yield to investigation if 

 it be treated on its own merits, without regard to the possibly, to all 

 appearances, contradictory phenomena presented by neighbouring 

 beaches, in which the beach-material, and the conditions of wave 

 and current action are not precisely the same. It is not, perhaps, 

 too much to say, that on no two contiguous beaches, nor at the two 

 ends of any one beach, are these conditions identical, though the 

 difference may be but slight. In Lyme Bay the difference in the 

 conditions of wave and current action on the eastern and western 

 beaches is very great. From near Sidmouth to Portland its shores 

 are more or less exposed to waves and currents generated in the 

 Atlantic, whereas no point, even in Start Bay, though upwards of 

 forty miles further down Channel, is similarly situated. Thus, 

 whilst the western beaches encounter their heaviest seas from the 

 eastward, the eastern beaches encounter their heaviest from the 

 westward, and there is no comparison between the power of the 

 waves in the two cases. Even so, the difference in vertical height 

 between the eastern and western beaches may seem unaccountably 

 great, though much of the difficulty vanishes when we remember 

 that the western waves act in concert with ocean-generated surface- 

 currents and an abnormally high water-level in the Channel, 

 whereas the eastern waves are only supplemented by a Channel 

 current, and have their action diminished by an abnormally de- 

 pressed water-level. 



