GLACIAL PERIOD. 
15 
Charpentier, but even shown that the north¬ 
eastern boundary of the ancient glacier of the 
Rhone was more extensive than was at first 
supposed. Other researches upon the ancient 
moraines along the shores of the Lake of 
Geneva, and in other parts of Switzerland, in 
which most geologists of the day took an ac¬ 
tive part, have made us as fully conver¬ 
sant with the successive outlines and varying 
extent of the principal glaciers ranging from 
the Alpine summits to the surrounding low¬ 
lands as we are with the glaciers in their 
present circumscription. But no one has 
done as much as Professor Guyot to add pre¬ 
cision to these investigations. The number 
of localities, the level of which he has deter¬ 
mined barometrically, with the view of fixing 
the ancient levels of all these vanished gla¬ 
ciers, is almost incredible. The result of all 
these surveys has been a distinct recognition 
of not less than seven gigantic glaciers de¬ 
scending from the northern and western slopes 
of the Alps to the adjoining hilly plains of 
Switzerland and France. It is most interest¬ 
ing to trace their outlines upon a recent map 
of those countries, but it requires that kind of 
