James Geikie — On Changes of Climate. 23 



In the Cwm Llafar and adjacent areas, this drift may be traced 

 upwards, as Professor Kamsay has shown, to 2300 feet above the 

 sea, and I believe to a greater height. In Cwm Llafar there are 

 terraces " the result of marine denudation during pauses in the re- 

 elevation of the country" (Ramsay). These terraces, so far as I 

 could see, are similar to thousands of platforms and scarps which 

 diversify hill-slopes in various parts of England. They are not so 

 regular, horizontal, or continuous, as those terraces which can be 

 traced to an artificial origin. With great interest, as might be 

 expected, I gazed on the long narrow channel, evidently ploughed 

 out by a glacier in the drift, as Professor Eamsay has shown. In 

 some places it is as fresh-looking as if it had been excavated within 

 the memory of man. Here, as in hundreds of other spots in Wales 

 and the Lake District, we have clear proofs that since the Glacial 

 period even rapid and good-sized /res7M«afer streams Tiave not lowered 

 the level of the valleys they traverse more than a few feet. 



Professor Eamsay, in his " Old Glaciers of North Wales," p. 101, 

 has drawn attention to a very important fact. Freshwater streams 

 cannot remove (and it follows that they cannot deposit) drift consist- 

 ing of a mixture of huge boulders with finer detritus. They wash 

 away the finer and lighter matter and leave a concentration of 

 boulders behind. But, it may be remarked, if freshwater could not 

 have accomjDlished the clearance of boulder drift so strikingly in- 

 dicated by the long narrow hollow in Cwm Llafar, how could it have 

 transported the blocks, the abstraction of which has left the magnifi- 

 cent mural cliff" at the head of the cwm. Freshwater is now assisting 

 frost and gravitation in demolishing this cliff, but it is clearly unable 

 to carry away the talus of fallen fragments. 



P.S. — Since the above was written, I have discovered a number of 

 very large boulders, chiefly Eskdale granite, at a height of very 

 nearly 1000 feet above the sea, on Eaw Head, one of the Peckforton 

 Hills, which rise suddenly out of the plain of Cheshire. I have also 

 found calcareous incrustations on a stone from the Colwyn Upper 

 Clay, and on numerous stones from the Upper Clay of Cheshire. 

 They look like the remains of Serpulce. [Specimens sent by Mr. 

 Mackintosh to the Editor for inspection were certainly not of organic 

 origin, but calcareous incrustations only, deposited by water charged 

 with carbonate of lime. — Edit. Geol. Mag.] 



V. — On Changes of Climate dttking the Glacial Epoch. 



By James Geikie, F.E.S.E., 

 District Surveyor of the Geological Survey of Scotland. 



Second Paper. 



IN the Magazine for December ^ I gave a brief outline of certain 

 phenomena connected with the Scottish Till, the chief aim of 

 my paper being to insist that beds of clay, sand, and gravel frequently 

 occur in that deposit, and that we can no longer consider these as 

 either insignificant or accidental. I also showed that while some of 



1 pp. 545-553. 



