Vol. 65.] GLACIAL EROSION IN NORTH WALES. 301 



this point is narrated by Mr. E. C. Andrews, of Sydney (New South. 

 Wales), who had become familiar with the forms producible in a 

 cycle of normal erosion, from his studies in the New England 

 district of North-Eastern Australia, and had become persuaded of 

 the systematic sequence in their development, before he saw the 

 intensely glaciated fiords of New Zealand, which at once impressed 

 him as beyond explanation by normal processes (1904). My own 

 experience was somewhat of the same kind ; for, although familiar for 

 many years with glaciated lowlands and low uplands in the northern 

 part of the United States, my first serious studies in the Alps did 

 not come until after I had seen the non-glaciated parts of the 

 Appalachian system and had become convinced of the verity of a 

 systematic sequence in the development of normally eroded forms. 

 When, with these features and principles in mind, I saw in 1899 

 the hanging lateral valleys over the wide-open main valleys of the 

 Alps, the abnormal relation stood forth as something so striking 

 and exceptional as completely to overturn my previous opinion that 

 glaciers were not strong erosive agents. 



On the other hand, one who studies the mountains of North 

 Wales, or other glaciated regions, without reference to non-glaciated 

 mountains and without consideration of the theoretical aspects of 

 normal mountain-sculpture, may very likely see nothing particularly 

 abnormal in his field of observation, and may regard the method of 

 discussion here adopted as unsafely based on hypothetical matter ; 

 indeed, as departing dangerously far from the safe ground of 

 immediately observable fact. But observers who are as familiar 

 with mountains of normal sculpture as with mountains of abnormal 

 sculpture, and who, through extended experience in districts of 

 different stages of development, have come to have confidence in 

 the scheme of the regular succession of forms produced in the ideal 

 cycle of erosion, will probably agree that, in a problem such as 

 we have here in hand, it is highly desirable, not to say essential, to 

 reason out the sequence of forms appropriate to normal processes, 

 to confirm the accuracy of the reasoned sequence by appropriate 

 observations, and to bear the confirmed sequence constantly in 

 mind. Otherwise, when a glaciated district like that around 

 Snowdon is under examination, there will be great danger of 

 ■confusing forms of abnormal and normal origins. 



It has sometimes seemed as if Ramsay's influence in this respect 

 had not been altogether favourable ; for, far from pointing to the 

 valleys of Wales as abnormal features, he repeatedly instanced 

 them as chiefly the work of normal erosion. He wrote : — 



* By denudations, chiefly subaerial since that time [New Eed Sandstone], the 



details of the present outlines of Wales have, I think, been produced 



There has been plenty of time for the cutting out of valleys in old table-lands 

 by the weather, by running water, and by glaciers ' (1866, pp. 236-37 ; 1881 , 

 pp. 328-29) ; 



and again : — 



' By far the greater part of [that] valley excavating-work was performed between 

 Permian and pre-glacial times The work of the glaciers of the last 



