THE QUATERNARY PERIOD IN EUROPE. 



571 



has been traced. It passed through Cornwall, across Dover Strait, 

 through Middle G-ermany and Southern Russia to the Ural Mountains, 

 following nearly the 50th parallel of latitude. In Fig. 939 we give the 

 outline of Western Europe if raised only 600 feet. The elevation was 

 much more. 



At the same time, the whole Alpine region of Middle Europe, al- 

 though beyond the limits of the ice-sheet, was mantled with snow to a 

 degree much greater than at present, and developed glaciers on a pro- 

 digious scale. Some of these have been traced out with great care and 

 skill. Especially has this been done for the great Rhone glacier by 

 Guyot, and more recently by Favre. At that time a great glacier came 

 down the valley of the Rhone, emerged on the plains, and filled the 

 whole valley of Switzerland, fifty miles wide, between the Alps and the 

 Jura, forming a great mer de glace 50 miles wide, 150 miles long, and 

 4,000 to 5,000 * feet deep. A figure is given below of this great glacier. 

 The dotted lines show the direction of motion as determined by 

 bowlders left in the valley or stranded high up on the slopes of the 

 Jura. 



Fig. 940 —Map showing the Outline and Course 

 of Flow of the Great Rh6ne Glacier (after 

 Lyell). 



Fig. 941. — Map showing the Lines of Debris ex- 

 tending from the Alps into the Plains of the 

 Po (after Lyell). 



Lakes Geneva and Neufchatel were filled and their bottoms scoured 

 by this great glacier. 



At the same time, also, on the southern slopes of the Alps, long 

 glaciers stretched out on the plains of Lombardy, as shown by the pro- 

 digious piles of debris (moraines) still left. Some of these moraines 

 are 1,500 feet high. Fig. 935 is a map of these lines of debris. 



* Archives des Sciences, vol. lviii, p. 159, 1877, and vol. iii, p. 228, 1880. 



