'226 GEOLOGY [CHAP. 



Letter 560 [to] the valleys of New South Wales) were formed exclusively 

 by fresh water. He underrates the power of sea, no doubt, 

 but read his remarks on valleys in the Sandwich group. 

 I came to the conclusion in ,S. America (p. 67) that the 

 main effect of fresh water is to deepen valleys, and sea to 

 widen them ; I now rather doubt whether in a valley or 

 fiord . . . the sea would deepen the rock at its head during 

 the elevation of the land. I should like to tour on the W. 

 coast of Scotland, and attend to this. I forget how far 

 generally the shores of fiords (not straits) arc cliff-formed. 

 It is a most interesting subject. 



I return once again to Coral. I find he does not differ 

 so much in detail with me regarding areas of subsidence ; his 

 map is coloured on some quite unintelligible principle, and 

 he deduces subsidence from the vaguest grounds, such as 

 that the N. Marianne Islands must have subsided because 

 they are small, though long in volcanic action : and that the 

 Marquesas subsided because they are penetrated by deep 

 bays, etc., etc. I utterly disbelieve his statements that most 

 of the atolls have been lately raised a foot or two. He does 

 not condescend to notice my explanation for such appear- 

 ances. He misrepresents me also when he states that I 

 deduce, without restriction, elevation from all fringing reefs, 

 and even from islands without any reefs ! If his facts are 

 true, it is very curious that the atolls decrease in size 

 in approaching the vast open ocean S. of the Sandwich 

 Islands. Dana puts me in a passion several times by 

 disputing my conclusions without condescending to allude 

 to my reasons ; thus, regarding S. Lorenzo elevation, he 

 is pleased to speak of my " characteristic accuracy," l and 

 then gives difficulties (as if his own) when they are stated 

 by me, and I believe explained by me whereas he only 

 alludes to a few of the facts. So in Australian valleys, he 

 does not allude to my several reasons. But I am forgetting 

 myself and running on about what can only interest myself. 

 He strikes me as a very clever fellow ; I wish he was not 

 quite so grand a generaliser. I see little of interest except 

 on volcanic action and denudation, and here and there 

 scattered remarks ; some of the later chapters are very bald. 



1 Dana's Geology (Wilkes expedition), p. 590. 



