1840 ivsi] EARTH- MOVEMENTS lig 



tions. The two first chapters will, I think, be prett; I, letter 481 



on the great gravel terraces and plains of Patagonia and Chili 

 and Peru. 



I am astonished and grieved over D'Orbigny's ' nonsense 

 of sudden elevations. I must give you one of his cases: He 

 finds an old beach 600 feet above sea. He finds still attached 

 to the rocks at 300 feet six species of truly littoral shells. 

 He finds at 20 to 30 feet above sea an immense accumulation 

 of chiefly littoral shells. lie argues the whole 600 feet up- 

 lifted at one blow, because the attached shells at jOO feet 

 have not been displaced. Therefore when the sea formed a 

 beach at 600 feet the present littoral shells were attached to 

 rocks at 30c feet depth, and these same shells were accumu- 

 lating by thousands at 600 feet. 



Hear this, oh Forbes. Is it not monstrous for a professed 

 conchologist ? This is a fair specimen of his reasoning. 



One of his arguments against the Pampas being a slow 

 deposit, is that mammifers are very seldom washed by rivers 

 into the sea ! 



Because at 12,000 feet he finds the same kind of clay with 

 that of the Pampas he never doubts that it is contemporaneous 

 with the Pampas [debacle ?] which accompanied the right 

 royal salute of every volcano in the Cordillera. What a pity 

 these Frenchmen do not catch hold of a comet, and return to 

 the good old geological dramas of Burnett and Whiston. 1 

 shall keep out of controversy, and just give my own facts. 

 It is enough to disgust one with Geology; though I have 

 been much pleased with the frank, decided, though courteous 

 manner with which D'Orbigny disputes my conclusions, given, 

 unfortunately, without facts, and sometimes rashly, in my 

 journal. 



Enough of S. America. I wish you would ask Mr. Horner 

 (for I forgot to do so, and am unwilling to trouble him again) 



1 D'Orbigny's views are referred to by Lyell in chapter vii. of the 

 Principles, Vol. I. p. 131. "This mud \i.e. the Pampean mud] contains 

 in it recent species of shells, some of them proper to brackish water, and 

 is believed by Mr. Darwin to be an estuary or delta deposit. M. A. 

 D'Orbigny, however, has advanced an hypothesis . . . that the agitation 

 and displacement of the waters of the ocean, caused by die elevation of 

 the Andes, gave rise to a deluge, of which this Pampean mud, which 

 reaches sometimes the height of [2,000 feet, is the result and monument," 



