THE FORMER EXTENSION OF GLACIERS. I 5 I 
especially when the water is free from sand. The 
scratches follow the general direction of the valley, 
the polished surfaces are on the weather side, and 
the lee side is the most abrupt, as in Fig. 36. A 
good example of such smoothed rocks may be seen 
just in front of the great Hotel at the Maloja. 
Giants’ Caldrons. 
Giants’ caldrons are sometimes assumed to be 
evidence of ancient glacier action. Those at Lucerne 
doubtless are so, but in other cases similar hollows 
have been produced by river action. 
Evidence derived from the Flora and Fauna. 
Another class of evidence is that derived from 
botany and zoology. Many of the plants now occupy- 
ing the Swiss mountains are indigenous to the Arctic 
regions. They could not under existing circum- 
stances cross the intervening plains, but must have 
occupied them when the climate was colder than it 
is now, and been driven up into the mountains, like 
the Marmot and the Chamois, as the temperature 
rose. The Arctic Willows, the Larch, and Arolla pine, 
for instance, are Siberian species, and do not occur 
in Germany. 
