TRANSACTIONS OF SECTION C. 883 



On some Dinosaurian Remains from the Oxford Clay 

 of Northam,pton. By C. W. Andrews. 



TUESDAY, SEPTEMBER 13. 

 The following Papers and Reports were read : — 



1. Restoration hy Charles Knight of the Extinct Vertebrates Bronto- 

 saurus, Phenacodus, Coryphodon, Teleoceras. By Professor H. F. 



OSBORN. 



2. The Work of Encrusting Organisms in the Formation of 

 Limestone. By'E. Wethered. 



3, The Action of Waves and Tides on the Movement oj Material on the 

 Sea Coast. By W. H. Wheeler, M.Inst.C.E., Boston, Line. 



The object of this paper is to show the relative effect of waves due to wind and 

 tidal action on littoral drift. 



It is pointed out that all cliffs that border the sea coast are doomed to erosion, 

 and the material derived from their destruction, after being sorted and prepared by 

 waves and tidal action, is conveyed to the depths of the sea. 



The function of wind waves is to break down the cliffs, to sort the material 

 displaced, and to reduce the larger rock fragments into sizes sufficiently small to 

 be acted on by the tides, and to disperse material that has been collected in large 

 masses by tidal action. 



The function of the tides consists in raising the water of the ocean sufficiently 

 high to enable the waves to attack the cliffs, in assisting in the grinding up of the 

 reduced rock fragments by their perpetual oscillating motion vmtil sufficiently 

 reduced in size, and then in transporting them to the bed of the sea, the latter 

 operation being effected either in solution, suspension, or rolling along the bottom. 



It is shown that all material eroded from the cliffs is ultimately carried 

 seaward, and that the sea yields nothing to the land. The only agents capable of 

 transporting material of greater specific gravity than the water are the waves, and 

 their action, until they break on the shore, is merely one of undulation; and 

 therefore it is only the stones, shingle, or sand which lie shorewards of the point 

 where the wave breaks that can be carried forward on to the beach. On the other 

 hand, the slope of the beach being seawards, all material has a natural tendency to 

 work downwards under the action of gravity, this downward action being aided 

 by the undertow of the retiring shore waves. 



Material eroded from the cliffs consists of rock fragments, boidders, sand, and 

 alluvium. The alluvium, consisting of particles of sufficient minuteness to remain 

 in suspension for a considerable time, is diffused by the waves over a very 

 considerable distance, and is finally deposited in the deep part of the ocean ; the 

 sand is gradually worked down the beach by the action of the waves and tides, 

 and is also spread over the sea bed, but nearer to the shore ; the rock fragments 

 are reduced to shingle small enough to be acted on by the tides, and in this 

 condition are rolled up and down the beach and drifted along the coast until 

 ground into particles sufficiently fine to be transported to the sea. Shingle is 

 generally accumulated in banks in the zone lying between low water of neap 

 tides and high water of spring tides, and travels along the coast in one given 

 direction. The heaping up and travel of the shingle is due to tidal action. The 

 effect of wind waves due to gales is principally destructive to shingle banks, 



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