cliffs, being permanently bathed and saturated in sea-water, would be 

 completely protected from subaerial weathering, quite gentle waves 

 would be sufficient to remove the debris, resulting in wide, flat benches 

 (1916, 1935). 



Peneplanation 



Thus we see that it was a very different thing to imagine the sea 

 operating mainly as a mechanical (and localty chemical) removal agent 

 in the inter-tidal belt, from having its active mechanical erosion reaching 

 right down to the ultimate wave-base. The sea could not act as an agent 

 of regional peneplanation according to the former concept, but could 

 according to the latter. With the former, the horizontal platform 

 of erosion would eventually grow so wide that the sea could no longer 

 wash away the debris but with the latter the waves would continuously 

 be working downwards, permitting powerful waves to reach the cliff. 

 It was this stumbling block which brought Douglas Johnson up against 

 the old teachings of Ramsay, von Richthofen, and many others — e.g., 

 de Martonne, de Lapparent, Kayser, including Gulliver and Scott, in 

 his own country, to name only a few outstanding names. De Martonne 

 (1934, p. 671 et seq.) refers in fact to the Ramsay-Richthofen school 

 versus the Barrell- Johnson school. The former believed that marine 

 erosion acting on a stable continent would eventually form such a 

 broad shallow abrasion platform that it would come to a standstill. 

 The Johnson school imagined that an entire continent might in time be 

 reduced to a submarine peneplain. 



To quote Johnson's own words (1919, and even in his revised edition 

 1938, p. 163) : " If a land stands still long enough, the waves will reduce 

 it to an ultimate abrasion platform ... no matter how great 

 ma;y have been the original extent of the land." Theoretically true 

 . . . perhaps, but R. T. Chamberlin (1930) has shown that if 

 all the lands were baseTevelled in this way the sea-level would rise 

 670 ft. ; so the production of such a horizontal peneplain is in any case 

 impossible. 



This Johnson concept is utterl}- unacceptable to de Martonne (1934, 

 p. 677) and most continental European students. De Lapparent made the 

 interesting suggestion that since wave action is far more impressive on 

 the stormy coasts of Great Britain (and we might add Johnson's own 

 New England shore-line) they should not automatically be regarded as 

 normal (De Lapparent, 1906, p. 242). Even then he contended that 

 the " normal " platform of marine erosion only ranges from high to 

 low-tide, level, though he called in storm- wave seasons, &c., to account 

 for series of terraces (a phenomenon now adequately explained by 

 eustatism). Park, in New Zealand, also made this point (1925), indicating 

 that subaerial solvents provided a " powerful ally " to the " Vriore 

 apparent " forces of mechanical erosion. 



In complete contrast to the fundamental teachings of the Lyell- 

 Johnson school, the recognition of the slowness of marine erosion has 

 apparently always been made in Europe. More recently, Novak (1938), 

 Bourcart (1938), Francis-Boeuf (1938), and others have concluded that 

 the continental shelf could not be due any more to Johnson's marine 

 erosion than it could be exclusively due to Sir John Murray's sedimentary 

 explanation (1888). Being left with subaerial erosion as the only satis- 

 factory answer to the abundant evidence now available, from the topo- 

 graphy (shown by sonic sounding), from the numerous basement rock 



355 



