THE ICE AGE. CLIMATE AND TIME. 
237 
is proved most conclusively by the effects which are seen to 
result from the fluctuations in the dimensions of existing glaciers. 
Professor Ramsay * informs us that, since the year 1767, the 
glacier of La Brenva rose 300 feet above its present level, and 
again declined, and the terminal moraines of the Rhone glacier 
arranged concentrically, one within another, bear witness to its 
recent gradual diminutions. The great Gorner glacier of Monte 
Rosa is even now steadily advancing, and is said, within the 
memory of men not old, to have already swallowed up forty 
chalets and a considerable tract of meadow land. He continues 
to remark, that such historical variations in the magnitude of 
glaciers are trifling, compared with their wonderful extensions 
in prehistoric times. In the Alps we find numerous instances 
of the former presence of glaciers where none now exist. “ So 
startling indeed are these revelations, that for a time the observer 
scarcely dares to admit to himself the justness of his conclusions, 
when he finds in striations, moraines, roches moutonnees and 
blocs perches , unequivocal marks of the former extension of an 
existing glacier, more than a long day’s march beyond its present 
termination ; and further, that its actual surface of to-day is 
even 2,000 feet and more beneath its ancient level.” 
The careful student of these striking indications will, as he 
ascends the mountain slopes, observe rounded slopes and striated 
contours to considerable heights above him, plainly marking 
the breadth and height of the glacier at early periods of its 
history, and in the uppermost regions the serrated and weather- 
worn crags that form the lips of the valleys, now almost bare 
of snow, still define the upward limits where the solid flowing 
ice in old times ceased to grind the rocks. Beyond this we 
know that all glaciers deepen their beds by erosion. The 
enormous weight of the mass of ice moving with irresistible 
power must tend to grind the surface upon which it moves, and 
thus cut out channels, and even scoop out lakes from its bed. 
Indeed, the general origin of lakes has been referred by Professor 
Ramsay to glacial action, and his hypothesis is supported by 
evidences which appear to be almost conclusive. 
The evidences marked upon the rocks of the globe are the 
only records which remain of the influences to which they have 
been subjected in past ages ; and, it is only by a proper under- 
standing of the events embodied in these 64 sermons in stones ” 
that the geologist can hope to give any real value to his 
deductions. It has been well said by Mr. Croll, in his re- 
markable book “ Climate and Time ” : — 
“No amount of description, arrangement and classification, 
however perfect or accurate, of the facts which come under the 
“The Old Glaciers of Switzerland and North Wales.’ 
