28 
GLACIAL PERIOD. 
Switzerland, as I have stated, one may trace 
the glaciers by their moraines, by the masses 
of rock they have let fall here and there, by 
the drift they have deposited, to the very foot 
of the opposite chain, where they have dropped 
their boulders along the base of the Jura. 
Ascending that chain, one finds the grooved, 
polished, and scratched surfaces to its summit, 
on the very crest of which boulders entirely 
foreign to the locality are perched. Follow the 
range down upon the other side and you find 
the same indications extending into the plains 
of Burgundy and France beyond. 
With a chain of evidence so complete, it 
seems to me impossible to deny that the whole 
space between the opposite chains of the Alps 
and the Jura was once filled with ice ; that this 
mass of ice completely covered the Jura, with 
the exception of a few high crests perhaps, 
rising island-like above it, and mounted to a 
height of some nine thousand feet upon the 
Alps, while it extended on the one side into 
the northern plain of Italy, filling all its de¬ 
pressions, and on the other down to the plains 
of Central Europe. The only natural inference 
from these facts is, that the climatic conditions 
