THE EARTH'S SURFACE SEA ACTION. 53 



back the upper. In such accumulations the assistance 

 rendered by cracks and other shrinkage fissures seems 

 to be at a minimum, as marine action at the base of a 

 drift cliff washes out the clayey matrix and carries 

 away the rest, while the upper portion is disintegrated, 

 causing the contained pebbles and blocks to drop out. 

 If the cliff is exposed to the sun or a dry wind, the 

 surface of the drift will necessarily crack; but regular 

 systems of joints are rarely formed. In some places, 

 however, generally with wide intervals between each, 

 there are joints or faults. These, if perpendicular, or 

 nearly so, to the line of cliff, are being worked along by 

 the sea and the atmospheric agencies, and form cooses 

 or small bays. Soft sandstones, conglomerates, or the 

 like, may be worked similarly to hardened gravel and 

 be cut into perpendicular cliffs. 



In the vicinity of the sea, meteoric abrasion would 

 seem to be more active than inland. On the coast 

 of Cork the slate beds at the coast are much more 

 weathered than elsewhere, since the sheet of ice that 

 once covered that county has melted away. Inland 

 the slates are ice-dressed, but in sea-cliffs the rock is 

 fast being denuded along the joints and cleavage lines, 

 so that the surfaces of the rocks may be compared to a 

 number of knife edges ranged alongside one another. 

 On the Arran Islands the limestone has weathered 

 away from four to six inches since the glacial period, 

 as proved by the unweathered pedestals of limestone 



