VIEWS OF ENGLISH WRITERS. 379 



shave it across and make a plain surface either horizontal or gently inclined. If a 

 country be sinking very gradually and the rate of waste by all causes be propor- 

 tionate to the rate of sinking, this will greatly assist in the production of the phe- 

 nomena we are now considering." 



When raised out of the water — 



" The streams made by its drainage immediately began to scoop out valleys, and, 

 though some inequalities of contour forming mere bays may have been begun by 

 marine denudation during emergence, yet in the main I believe that the inequali- 

 ties below the [level of the plain] have been made by the influence of rain and 

 running water." * 



Greenwood, an early advocate of the efficacy of " rain and rivers/' 

 (1857), directed his arguments against the prevailing belief of the tinie 

 that valleys were carved by marine currents, but does not seem to have 

 considered the possibility of producing plains by the long continued 

 weathering and washing of the land. 



The important paper by Jukes, on the " Formation of . . . river 

 valleys in the south of Ireland," f still finds many followers among 

 English geologists. Like Ramsay, Jukes assumed an uplifted plain of 

 marine denudation on which the rivers of today began their erosive work 

 (page 399), but he did not specify slow depression during the marine 

 denudation. 



Lyell said little on the problem before us. His " Principles" do not 

 discuss plains of denudation. His " Elements of Geology " X allow only 

 small valleys to stream work, and ascribe the larger valleys "to other 

 causes besides the mere excavating power of rivers " (page 70). It is said 

 that " denudation has had a leveling influence on some countries of 

 shattered and disturbed strata " (page 71). Again, " in the same manner 

 as a mountain mass may, in the course of ages, be formed by sedimentary 

 deposition, layer after layer, so masses equally voluminous may in time 

 waste away by inches ; as, for example, if beds of incoherent materials 

 are raised slowly in an open sea where a strong current prevails " (page 

 70). The problem of subaerial denudation here discussed was not then 

 formulated. 



The writings of Sir A. Geikie offer several interesting quotations. 

 When describing the general uniformity of the sky-line over the Scotch 

 Highlands in the first edition (1865) of the " Scenery of Scotland," he 

 writes : 



" In other words, these mountain tops are parts of a great undulating plain or 

 table-land of marine denudation. . . . The marine denudation probably went 



* Phys. Geol. and Geogr. Great Britain, 5th ed., 1878, pp. 497, 498. 

 t Quart. Joiirn. Geol. Soc, vol. xviii, 1862, pp. 378-403. 

 X 6th edition, 1868. 



