THE EARTH'S SURFACE SEA ACTION. 51 



influence on soft strata is very apparent; while in 

 places it seems to be the principal denudant, the sea 

 acting chiefly as a carrier. 



Margining the sea in south-east Ireland, there 

 extend, for miles, cliffs of marl which are being 

 constantly worn away, yet the sea seems to have 

 very little effect on them. Heat opens joints in the 

 marl, thereby leaving it a prey to meteoric abrasion ; 

 while the principal work the sea does is to act as a 

 carrier, and remove the debris brought down within 

 its reach. As in the case of the formation of chalk 

 escarpments previously mentioned, so here also, there 

 are forming two systems of joints that regulate 

 the denudation, one being nearly perpendicular, and 

 the other nearly parallel to the coast-line. In the 

 first, meteoric abrasion widens the joints and denudes 

 the marl into transverse ridges or pinnacles, the joints 

 being near together ; but if the joint lines are nearly 

 parallel to the coast-line, they become frequently 

 filled by the rain, and masses of the marl are forced 

 to slide outwards. Thus the denudation of the cliff 

 takes place from the top downward, and not from 

 the bottom upwards, as ought to be the case if the 

 sea was the principal worker. Extreme marinists 

 would claim these cliffs as seawork, and if eventually 

 the land is elevated and they form an inland escarp- 

 ment, extreme subcerialists would point to them as 

 due to meteoric abrasion ; while neither force unaided 



