from the northern plains, and down from the 
mountainsides to form vast hordes of fugitives 
hastening to southern plains. 
This hegira continuing as the sheet of ice grew 
and plowed its glacier beds slowly down to median 
latitudes of Europe and Asia, the entire members 
of many families were overtaken on the northern 
side of the mountain ranges and frozen out; 
others, passing between the ends of the ranges, 
reached the shores of the Mediterranean Sea and 
the Indian Ocean, and were then and there 
destroyed, a few only escaping by the narrow, 
devious Isthmus of Suez into Africa, while others 
huddled upon the three peninsulas of Arabia, 
Hindustan, and Malacca. 
On the Western Continent a great portion of the 
plants in their flight came down unobstructed, to 
the Gulf of Mexico, to be caught and frozen there, 
a few eastern families escaped on the peninsula of 
Florida, while the greater part of the western 
plants ran down along the plateau of Mexico into 
Central x\merica, and perhaps finally crossed on 
the Isthmus of Darien into South America. 
GREATER DESTRUCTION BY HEAT. 
Following the Glacial came a Thermal Age, with 
contrary effects, yet with more destructive results. 
The ice melts on the southern verge of the ponder¬ 
ous ice cover, allowing the plants to return, timidly 
seeking the newly-emptied glacier beds. Soon 
after, the flood-water sinking into the mountain¬ 
sides, the brown earth, becoming vivified, invites 
the grasses and flowers to new-made homes, while 
( 8) 
