i8 4 i 1880] GLEN ROY 193 



then water would escape from an outlet at Loch Spey, and Letter 530 

 the highest shelf would be first formed. Secondly, ice began 

 to retreat, and water will flow for short time over its surface ; 

 but as soon as it retreated from behind the hill marked Craig 

 Dhu, where the outlet on level of second shelf was discovered 

 by Milne, 1 the water would flow from it and the second 

 shelf would be formed. This supposes that a vast barrier 

 of ice still remains under Ben Nevis, along all the lower 

 part of the Spean. Lastly, I suppose the ice disappeared 

 everywhere along L. Loggan, L. Treig, and Glen Spean, 

 except close under Ben Nevis, where it still formed a barrier, 

 the water flowing out at level of lowest shelf by the Pass 

 of Mukkul at head of L. Loggan. This seems to me to 

 account for everything. It presupposes that the shelves were 

 formed towards the close of the Glacial period. I come up 

 to London to read on Thursday a short paper at the Linnean 

 Society. Shall I call on Friday morning at 9.30 and sit 

 half an hour with you ? Pray have no scruple to send a line 

 to Queen Anne Street to say " No " if it will take anything 

 out of you. If I do not hear, I will come. 



To J. Prestwich. Letter S3I 



Down, Jan. 3rd, 1880. 



You are perfectly right. 2 As soon as I read Mr. Jamie- 

 son's article on the parallel roads, I gave up the ghost with 

 more sighs and groans than on almost any other occasion in 

 my life. 



IV. CORAL REEFS, FOSSIL AND RECENT, 1841-81. Letter 532 



To C. Lyell. 



Shrewsbury, Tuesday, 6th [July, 1841]. 



Your letter was forwarded me here. I was the more glad 

 to receive it, as I never dreamed of your being able to find 

 time to write, now that you must be so very busy ; and I 

 had nothing to tell you about myself, else I should have 

 written. I am pleased to hear how extensive and successful 

 a trip you appear to have made. You must have worked 



1 See note 2 on Letter 521, p. 181. 



2 Prof. Prestwich's paper on Glen Roy was published in the Phil. 

 Trans. R. Soc. for 1879, p. 663. 



VOL. II, 13 



