450 Whitaker — On Suhaerial Denudation. 



the theory of suhaerial denudation : Dr. C. Le N. Foster and Mr. W. 

 Topley,^ who have worked out in detail the question of the Wealden 

 denudation, the latter having also touched on other districts f Mr. A. 

 Geikie,^ Mr. A. H. G-reen/ Mr. G. Maw/ Mr. A. E. Wallace,^ Mr. A. 

 B. Wynne/ and, to some extent, the Eev. 0. Fisher.* In far countries, 

 too, Professor Dana,» Professor Hind,^" Mr. J. P. Lesley," Sir W. 

 Logan,^^ Dr. Newhury,^^ and Professor Whitney,^* in America ; Dr. 

 Haast, in New Zealand /^ Mr. T. Belt, in Nova Scotia /« and Dr. 

 Eubidge, in South Africa,^'' have borne witness on the same side. 



It is remarkable that most of the subaerialists are of English race 

 (using that name in the broadest sense), but few foreign geologists 

 allowing that anything but the sea or a cataclysm can have given 

 rise to hills or valleys of large size ; and also that a great number 

 of these subaerialists are or have been employed on Government 

 Geological Surveys, and therefore have been accustomed to be con- 

 stantly in the field, earning their bread by their hammers, and 

 spending their days in the more or less detailed examination of the 

 geological structure and physical features of the districts which it 

 has been their duty to survey and describe. 

 3. — General Bemarhs. 



The following pages treat of escarpments and not of ordinary 

 valleys, because the formation of the latter by other agents than the 

 sea is now more generally understood. The same kind of argu- 

 ment holds in both cases, but the suhaerial cutting out of valleys 

 is at first sight clearer than that of escarpments, and perhaps is sup- 

 ported by more direct proof. 



1 Quart. Journ. Geol. Soc, vol. xxi. p. 443 (1865). 



2 Geol. Mag., Vol. III. p. 435 (1866), and Vol. IV. p. 184 (1867). 



3 Notes of Travel by Vacation Tourists, 1861. — The Geology and Scenery of 

 Scotland, (1865). 



I Geol. Survey Memoir on Sheets 81 N.W. and S."W., p. 86 (1866). 

 6 Geol. Mag., Vol. III. pp. 344, 439, 575 (1866). 



6 Quart. Journ. of Science, vol. iv. p. 33 (1867). 



T Mem. Geol. Survey, India, vol. v. p. 201 (1866).— Geol. Mag., Vol. IV. pp. 3, 

 345 (1867). 



8 Quart. Journ. Geol. Soc, vol. xvii. p. 1 (1861). 



9 United States Exploring Expedition during the Years 1838-42, vol. x., Geology, 

 4to., Philadelphia, 1849, pp. 384-92, 526-33, 670-7.— Manual of Geology, 8vo., 

 Philadelphia, 1863, pp. 635-42, 676. 



10 Quart. Journ. Geol. Soc, vol. xx. pp. 125, 126, 128-30 (1864), where references 

 to the author's other notes on the subject are given. 



II Notes on a Map to Illustrate Five Types of Earth- Surface, 4to., Philadelphia, 

 1866. 



12 Geol. Survey, Canada— Eept. of Progress to 1863, 8vo., Montreal, p. 889. 



^3 Part 3 (Geology) of Lieut. Ives' Eeport on the Colorada Eiver of the "West. 

 1861. Eeferences to other remarks on denudation by this author are given in Pro- 

 fessor Hind's paper referred to above. 



1* Eeport on the Geological Survey of the State of "Wisconsin, vol. i, pp. 117-26 

 (1862). 



15 Eeport on the Geology of Canterbury, New Zealand ;— and Quart. Journ. Geol. 

 Soc, vol. xxi. pp. 129, 130 (1865). 



16 Quart. Journ. Geol. Soc, vol. xx. p. 463 (1864)— in abstract only. The paper 

 has been printed in full in Trans. Nova Scotian Institute of Nat. Sci., Vol. I. Part 

 iv. p. 91. 



" Geol. Mag., Vol. III. p. 88 (1866). 



