1841— 1SS0] GLEN ROY 1 8 1 



theory of Agassiz and Buckland 1 : until I read your im- Letter 521 



portant discovery of the outlet in Glen Glaster 1 I never 

 thought this theory at all tenable. Now it appears to me 

 that a very good case can be made in its favour. I am not, 

 however, as yet a believer in the ice-lake theory, but I tremble 

 for the result. I have had a good deal of talk with Mr. Lyell 

 on the subject, and from his advice I am going to send a letter 

 to the Scotsman, it) which 1 give briefly my present impression 

 (though there is not space to argue with you on such points 

 as I think I could argue), and indicate what points strike me 

 as requiring further investigation with respect, chiefly, to the 

 ice-lake theory, so that you will not care about it. . . . 



P.S. — Some facts mentioned in my <. * S. America, 



p. 24,''' with regard to the shoaling of the deep fiords of 

 T. del Fuego near their mouths, and which I have remarked 

 would tend, with a little elevation, to convert such fiords into 

 lakes with a great mound-like barrier of detritus at their 

 mouths, might, possibly, have been of use to you with regard 

 to the lakes of Glen Roy. 



To C. Lyell. UMtcr $2a 



I > \s n, We Inesday, Sth. 

 Many thanks for your paper. 4 I do admire your zeal on 

 a subject on which you are not immediately at work. I will 



1 Agassiz and Auckland believed that the lakes which (brined the 

 "roads" were confined by glaciers or moraines. See "The Glacial 

 Theory and its Recent Progress," by Louis Agassi/, Edinb. New Phil. 

 Journ., Vol. XXXIII., p. 217, 1S42 (with map). 



• Mr. Milne discovered that the middle shelf of Glen Roy. which 

 Mr. Darwin stated wis "not on a level with any water-hid '(Darwin, 

 loc. cit., p. 43), exactly coincided with a watershed at the head of (den 

 Glaster (Milne, loc. cit., p. 398). 



3 The creeks which penetrate the western shores of Tierra del FuegO 

 are described as "almost invariably much shallower 'lose to the open 

 sea at their months thin inland. . . . This shoalncss of the sea-channels 

 near their entrances probably results from the quantity of sediment 

 formed by the wear and tear of the outer rocks exposed to the full force of 

 the open sea. I have no doubt that many Likes — for instance, in Scotland 

 — which are very deep within, and are separated from the sea appa- 

 rently only by a tract of detritus, were originally sea-channels, with banks 

 of this nature near their mouths, which have since been upheaved " (6V< .'. 

 Obs. S. America, p. 24, footnote). 



4 " On the Ancient Glaciers of Forfarshire.'' Pt\ . Vol. III. 

 p. yj, 1840. 



