120 Proceedings of the Royal Irish Academy. 



are very different, and the conditions under whidi they are exposed 

 are also variable. We soon perceive that the streams of the tide, to 

 the movement of which so much abrading power has been attributed, 

 have very little influence upon this coast ; that it is chiefly in those 

 places where the tides have little strength, but where the softer rocks 

 prevail, and the exposure to the prevalent winds, and hence to 

 breakers, is considerable, that the chief loss of land by the action of 

 the sea is greatest. In fact, the tides rarely run beyond one or two 

 miles per hour, except round the headlands, which are nearly all com- 

 posed of hard rocks, the softer parts of the coast having been hollowed 

 out by the breakers, during the lapse of ages, into creeks, coves, and 

 bays, so as to be removed from the main stream of the tide." 



It would be difficult to form a correct idea of the geological 

 time duiing which this coast has taken its present form, when we 

 perceive so many hard rocks worked into creeks and coasts, and learn 

 as indeed from their aspect we would expect, that no appreciable 

 change has been observed in them during the memory of man, we can 

 readily believe that the present condition of this coast is due to no 

 ordinary lapse of time as reckoned by him. 



(p. 436.) — " The hard quartzose and trappean rocks of Trevose 

 Head, the greenstone and trappean rocks of Pentire Point, near 

 Padstow, the hard slates of St. Agnes Head, the compact sandstones 

 and hard slates of Godrevy Head, the greenstone of St. Ives Point, 

 the greenstone and hardened schistose rocks of Giu'nards Head, and 

 the granite of the Land's End — may be readily supposed incapable of 

 being appreciably wasted by the action of the streams of tide which 

 pass over them. In like manner the granites of many other points in 

 the Land's End district." 



(p. 437.) — " A veiy short experience of the destructive effect of 

 breakers will be sufficient to afford evidence of the form which a 

 coast must take according to the variable manner in which it may be 

 exposed to them ; so that after the lapse of ages any given coast will 

 readily show, from the wearing away of the softer rocks into creeks, 

 coves, and bays — the harder being gradually left to protrude as points 

 and headlands — that it has been scooped out according to the unequal 

 resistances of the rocks on the one hand, and the variable power of 

 the breakers on the other, due allowance being made for the original 

 form of the land, and the indentations produced by the entrance of 

 the sea, at its high- water level, into valleys, producing estuaries." 



(p. 438.) — " It rarely happens that breakers do not fall on the 

 western part of the coast, even in the calmest weather, undulations 



