180 THE RIVER VALLEYS OF 



demonstration another force is actually performing. 

 At the present day the sea is denuding away the soft 

 rock, while, except in broken places, it does little 

 work on the hard Old Ked sandstones and grits. And 

 if it is capable of executing this work now, why was 

 it not able to do similar work in bygone ages ? And 

 the present work, if subsequently slightly modified 

 by meteoric abrasion, would be similar to the present 

 features of the adjoining valleys. 



Cork Harbour points out the process by which the 

 sea is prone to act, besides showing the share that 

 wind has in marine denudation. There the sea has 

 worked in along the principal -breaks, which in all 

 that part of the country bear about N. 20 W. The 

 sea having breached the softer strata, and having 

 thereby obtained access to the site of Cork Harbour, 

 its further operations were influenced by the prevailing 

 winds ; and as these blow principally from the west 

 and south-west, the greatest denudation was accom- 

 plished in the eastern arms of the estuary ; so that 

 now, although the sea is still carrying on its original 

 work along the N. 20 W. line of broken rocks, yet 

 the bay forming the harbour has been excavated 

 principally to the eastward of that line. Similar cut- 

 tings across hard strata with associated longitudinal 

 bays along the intervening soft strata occur in various 

 other places in that neighbourhood ; however, it is 

 unnecessary to multiply examples, as the work in all 



