192 GEOLOGY [CHAP. IX 



Letter 528 " Ne sutor ultra crepidam," I think, applies in this case to 

 him. I am hard at work on Variation under Domestication^ 



P.S.--I am rather overwhelmed with letters at present, 

 and it has just occurred to me that perhaps you will forward 

 my note to Mr. Jamieson ; as it will show that I entirely 

 yield. I do believe every word in my Glen Roy paper is false. 



Letter 529 T C L y elL 



Down, Oct. 20th [1861]. 



Notwithstanding the orchids, I have been very glad to 

 see Jamieson's letter ; no doubt, as he says, certainty will 

 soon be reached. 



With respect to the minor points of Glen Roy, I cannot 

 feel easy with a mere barrier of ice ; there is so much sloping, 

 stratified detritus in the valleys. I remember that you some- 

 where have stated that a running stream soon cuts deeply 

 into a glacier. I have been hunting up all old references 

 and pamphlets, etc,, on shelves in Scotland, and will send 

 them off to Mr. J., as they possibly may be of use to him 

 if he continues the subject The Eildon Hills ought to 

 be specially examined. Amongst MS. I came across a very 

 old letter from me to you, in which I say: " If a glacialist 

 admitted that the sea, before the formation of the shelves, 

 covered the country (which would account for the land-straits 

 above the level of the shelves), and if he admitted that the land 

 gradually emerged, and if he supposed that his lakes were 

 banked up by ice alone, he would make out, in my opinion, 

 the best case against the marine origin of the shelves." 2 

 This seems very much what you and Mr. J. have come to. 



The whole glacial theory is really a magnificent subject. 



Letter 530 To C. Lyell. 



Down, April ist [1862], 



I am not quite sure that I understand your difficulty, so 

 I must give what seems to me the explanation of the glacial 

 lake theory at some little length. You know that there is a 

 rocky outlet at the level of all the shelves. Please look at my 

 map. 3 I suppose whole valley of Glen Spean filled with ice ; 



1 Published 1868. 



2 See Letter 522, p. 185. 



3 The map accompanying Mr. Darwin's paper in the Phil. Trans, 

 R. Soc., 1839. 



