182 GEOLOGY [CHAP. IX 



Letter 522 give my opinion as briefly as I can, and I have endeavoured 

 my best to be honest. Poor Mrs. L)/ell will have, I foresee, 

 a long letter to read aloud, but I will try to write better than 

 usual. Imprimis, it is provoking that Mr. Milne l has read 

 my paper 2 with little attention, for he makes me say several 

 things which I do not believe as, that the water sunk sud- 

 denly ! (p. 10), that the Valley of Glen Roy, p. 13, and Spean 

 was filled up with detritus to level of the lower shelf, against 

 which there is, I conceive, good evidence, etc., but I suppose 

 it is the consequence of my paper being most tediously 

 written. He gives me a just snub for talking of demon- 

 stration, and he fights me in a very pleasant manner. Now 

 for business. I utterly disbelieve in the barriers 3 for his 

 lakes, and think he has left that point exactly where it was 

 in the time of MacCulloch 4 and Dick. 5 Indeed, in showing 

 that there is a passage at Glen Glaster at the level of the 

 intermediate shelf, he makes the difficulty to my mind greater. 6 

 When I think of the gradual manner in which the two upper 

 terraces die out at Glen Collarig and at the mouth of Glen 

 Roy, the smooth rounded form of the hills there, and the lower 

 shelf retaining its usual width where the immense barrier 

 stood, I can deliberately repeat "that more convincing 

 proofs of the non-existence of the imaginary Loch Roy could 

 scarcely have been invented with full play given to the 

 imagination," etc. : but I do not adhere to this remark with 

 such strength when applied to the glacier-lake theory. 

 Oddly, I was never at all staggered by this theory until 

 now, having read Mr. Milne's argument against it. I now 

 can hardly doubt that a great glacier did emerge from Loch 

 Treig, and this by the ice itself (not moraine) might have 

 blocked up the three outlets from Glen Roy. I do not, 



1 " On the Parallel Roads of Lochaber, etc." Trans. R. Soc. Edinb., 

 Vol. XVI., p. 395, 1849. [Read March ist and April 5th, 1847.] 



2 "Observations on the Parallel Roads of Glen Roy, etc." Phil. 

 Trans. R. Soc., 1839, p. 39. [Read Feb. 7th, 1839.] 



3 See note 3, Letter 521. 



4 " On the Parallel Roads of Glen Roy." Geol. Trans., Vol. IV., 

 p. 314, 1817 (with several maps and sections). 



5 "On the Parallel Roads of Lochaber." Trans. R. Soc. Edinb., 

 Vol. IX., p. i, 1823. 



6 See note 2, p. 181. 



