162 Mr. De la Beche's Notes o?i the Formation 



water sufficiently rapid to produce the attrition required to 

 give a round figure and smooth siu'face to hard and irregular 

 pieces of stone".* Although it is acknowledged that no tri- 

 turation of rock fragments into rounded gravel is now effected 

 in the bottom of the ocean, it has been supposed that gravels 

 formed or collected on the shores of continents or islands are 

 conveyed there, to be consolidated, and converted into beds of 

 conglomerate. An attention to the effects of seas on their 

 coasts will, however, show us that these gravels do not ti'avel 

 outwards into great depths, but that the ocean exerts its power 

 to throw them back upon the dry land whence they were de- 

 rived. Attention to a sea coast with a shingle beach during 

 a gale of wind will show this. Every breaker is more or less 

 charged with shingles, which are forced forward as far as the 

 broken wave can reach, and in their shock against the beach 

 drive others before them, that were not held in momentary 

 mechanical suspension by the breaker. By these means, and 

 particularly at the top of high-water, the shingles are projected 

 on the land beyond the reach of retiring waves. Heavy gales 

 and high tides combined seem to produce the highest beaches; 

 they do indeed sometimes cause breaches in the ramparts 

 they have raised against themselves, but they quickly repair it. 

 The great accumulation of beach upon the land being effected 

 at the height of the tide, when the tide ebbs, it is quite clear 

 the sea cannot deprive the land of what it has thrown upon it. 

 In moderate weather and during neap tides various little lines 

 of beach are formed, which are swept away by a heavy gale; 

 and when these little beaches are so obliterated, it might be 

 supposed by a casual observer that the sea was diminishing the 

 beach ; but attention will show that the shingles of the lines, 

 so apparently swept away, are but accumulated elsewhere. 

 These remarks of course only apply to such situations where the 

 sea, during gales, has no access to clifts or piers, from whence 

 there might be a back-wave carrying all before it ; but to such 

 situations, and they are abundant, where the breakers meet 

 with no resistance, and strike nothing but the more or less in- 

 clined plane of a shingle beach. Even in cases where the waves 

 in heavy gales and high tides do reach cliffs, and for the time 

 remove shingle beaches, it is curious to see how soon these lat- 

 ter are restored when the weather moderates, and when the 

 breakers, in consequence of a diminished projecting force, cease 

 to recoil from the cliff behind. 



Shingle beaches travel in the direction of the prevalent winds, 

 or those which produce the greatest breakers; of this, excel- 



• Illustrations of the Huttonian Theory, p. 7. 



lent 



