48 8 Coast-cliff Denudations. 



island forms a portion of an extensive tableland, which 

 is continued far into the mainland of Pembrokeshire, 

 broken on\y by minor hills formed of hard igneous 

 rocks which have more effectually resisted denudation, 

 while far to the south the islands of Skomer and Skok- 

 holm continue the outlines of the upland plain, such as 

 in Chapter XXX. I have called an old plain of marine 

 denudation. 



All along the west coast, where solid rocks prevail, 

 the hardest masses usually form promontories, while the 

 bays have been scooped in softer material ; and this fact, 

 though the rate of waste may not be detected by the 

 eye in many years, yet proves the nature of marine and 

 atmospheric denudation when combined on coast cliffs. 

 The very existence of sea cliffs proves marine denuda- 

 tion, for the strata that form these cliffs come abruptly 

 to an end in precipitous escarpments. To see this in 

 perfection let any one walk along the coast cliffs formed 

 of Old Eed Sandstone near Arbroath in Forfarshire. 

 There the broad inland plain ends abruptly in vertical 

 precipices, that rise from 150 to 250 feet above the 

 waves at their base, and while the tide is retreating to 

 its completest ebb, long reefs and skerries of hard 

 edged strata tell of the progressive cutting back of a 

 great modern plain of marine denudation, similar to 

 that old one which stretches inland from the high edge 

 of the existing cliff. 



The Needle-rock near Fishguard, the Needles of the 

 Isle of Wight, and many other rocky c stacks' form 

 excellent cases in point, standing a little aloof from the 

 high cliffs of rock that form the shore-line ; and the 

 Orkney Islands themselves are only fragments of an 

 older land separated by denudation from the mainland 

 of Scotland. While being deposited. Nature never 



