GLACIAL PERIOD 



295 



Some of the most appalling disasters of the sea have been 

 due to ships colliding with icebergs. 



Glacial Period. Careful examination of all the surface 

 formations over large areas of what are now the most thickly 

 populated regions of North America and Europe has led 

 geologists to believe that at a former period in the earth's 

 history, perhaps not more than a few thousand years ago, 

 the northern part 

 of both continents 

 was covered with a 

 thick layer of ice. 

 Evidences of this 

 ancient ice covering 

 are seen in North 

 America as far south 

 as the Ohio River 

 and extending over 

 a vast region which 

 now enjoys a tem- 

 perate climate. This 

 mantle of ice after 



several advances and retreats finally disappeared, leaving 

 the country as we now find it. 



Although the border to which the ice extended and many 

 of the changes which the ice made in the surface of the 

 country have been carefully studied and mapped, yet 

 the cause of this extension of the ice and the exact time 

 at which it occurred have not yet been determined. Many 

 theories have -been brought forward to account for it, but 

 none of them explains all the facts. 



That the ice was here seems to be sure, but exactly when 



A BOWLDER BORNE ALONG ON TOP OF A 

 GLACIER 



Notice the size as compared with the umbrella. 



