46 Correspondence — Mr, Whitaker, 



in Britain, and no bones of mammals, proves them to be much 

 newer than the neighbouring deposits containing older forms of 

 life." Now, since writing you I have heard from Mr. Prestwich 

 that he found the land and freshwater shells of the Erith beds 

 in this cutting in the year 1850 or 1851, and among them, he 

 thinks, the Cyrena fluminalis. Mr. Whitaker, also writes me, in 

 reply to my enquiry, that he thinks he found the Cyrena in the 

 cutting West of Dartford Station some years ago, but cannot speak 

 with any certainty, not having his note books of that date with 

 him. S. V. W., JuN. 



SUBAERIAL DENUDATION. 



Sm, — I did not intend to answer communications objecting to 

 arguments and statements in my paper ; but one of the letters in 

 your last number demands a few words. 



I am sorry that I should have misrepresented the views of my 

 friend and colleague, Mr. Hull, and thereby given him any annoy- 

 ance ; but, at the same time, I am glad that the name of another 

 able and tried geologist may be added to the roll of those who allow 

 that great things have been done by subaerial denudation, though he 

 does not go so far as some of us, 



I read his letter on " Kiver-Denudation of Valleys," soon after it 

 appeared (Geological Magazine, Vol. III., p. 474) but did not refer 

 to it in my paper, as it seemed to me to uphold marine rather than 

 subaerial denudation. My mistake arose from taking certain state- 

 ments of Mr. Hull's, which had reference to some valleys of a certain 

 sort, as applying to valleys generally. 



I have not seen his paper in the " Popular Science Eeview," and 

 I do not hold myself bound to wade through journals of that kind, in 

 search of original articles on geology.^ 



There is another geologist to whom justice was not done in my 

 paper (p. 450) — the Eev. 0. Fisher, who, I believe, first published 

 the second of those arguments against the marine formation of escarp- 

 ments that Sir Charles Lyell admits to be unanswerable (p. 449). 



The remarks of your correspondents seem to me to divide them- 

 selves, for the most part, as follows: — (1). Some show that, as 

 might be expected (man being fallible), I have overlooked sundry 

 small matters ; (2) some make statements of a kind that I have not 

 denied or objected to at all ; (3) some have been already answered 

 in my paper ; (4) some are simply exceptions to rules that I have 

 stated to be general, not universal (and according to the old proverb 

 " the exception proves the rule") ; (5) some are founded on a strange 

 misunderstanding of the arguments of subaerialists ; (6) some are 

 statements that I cannot agree to, and which I can only meet by 



1 Mr. Hull's criticism (Geol. Mag., Vol. IV., p. 567,) of a sentence in the first 

 part of Mr, Whitaker's paper, "On Subaerial Denudation," (p. 453) should have 

 been omitted, as the sentence objected to was corrected at the end of second part 

 (p. 493), a month before Mr. Hull's letter appeared — by the insertion of the word 

 "us," after "follow" (line 15, p. 453).— Edit. 



