Revieiv and Comment. 
359 
smooth, the rugged hill has been reduced to rounded slopes of 
rock (like the rounded backs of plunging dolphins). But the 
crag remains a crag, the buttress a buttress, and the hill a hill. 
The valley also does not alter its leading outlines; all that the 
ice has done has been to act like a gigantic rasp; it has modi¬ 
fied, not revolutionized; it has moulded, not regenerated. 
No sooner do we come to study in detail the effects of the 
ancient glaciers in the upper valleys of the Alps, than we are 
struck by their apparent inefficiency as erosive agent. The 
result of prolonged personal study of the Alps may be summed 
up in these words: 
“Valleys appear to be much older than the ice age; and to 
have been but little modified during the period of maximum 
extension of glaciers. 
“Extensive valley tracts have been uncovered by the recent re¬ 
treat of the Alpine glaciers, but nowhere has evidence been found 
of excavation as distinguished from abrasion. No signs what¬ 
ever that the glaciers were able to break off or root up blocks of 
rock from their beds, were seen. The ice seemed to wear off 
prominences only. Cases were observed wdiere the ice had 
flowed over large blocks of loose rock and had striated them on 
top and on both sides but had not moved them. ” 
He points out that the alpine lakes are near the ends of the 
ancient glaciers, not farther up where the ice must have been 
thicker and lasted longer. 
He notes also that the Italian lakes have radiating arms which 
indicate other than glacial origin. 
He concludes that rock basins are original valleys of erosion 
modified by earth movements. 
No mention is made by Professor Bonney of the blocking up 
of valleys by drift although it is clear that the amount of crust 
movement (subsidence) necessary to account for the alpine lakes 
would be much less on the supposition that the ice borne debris 
had choked the valleys to some extent near the ice front. 
A review is given by Prof. Bonney in Nature vol, 47, p. 5, 
of a most important work, perhaps the most important of 
all yet undertaken, in relation to the question in hand, during 
the last thirty years. The work reviewed is volume one of a 
monograph of Lake Geneva by Prof. F. A. Forel. 8 * 
36 Le Leman, Monographic Limnologique; F. A. Forel, Tome Premier 
(Lausanne, F. Rouge, 1892.) 
