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T/ze Greaf B/we Heron, one of the commonest waders in the East, has a wing span as great as 

 an eagle's. It winters in the South but individuals may stay about the Heartland all year round. 



great domed slab of most ancient and almost non-compressible 

 rocks that spreads all across eastern Canada; the whole of the 

 Quebec-Labrador Peninsula; the Gulf of St. Lawrence; New- 

 foundland; Nova Scotia; and the whole of New England. To the 

 west it spread over the Canadian Lakes District (see Chapter 3) 

 from the Keewatin Peninsula. A great part of this, notably the 

 Laurentian Shield, Labrador, and the lands about the mouth of 

 the St. Lawrence, did not sink to anything like the same extent 

 as surrounding areas. The greatest sag was under Hudson Bay; 

 the next greatest sag occurred in the area south of the Laurentian 

 Shield over what is now known as the Great Lakes. 



Evidence that all this territory was once covered with ice is 

 plain to see, once the things to look for have been pointed out 

 by geologists. These may be divided into two lots; those produced 

 on the land actually covered by the icecap, and those to be seen 

 on lands beyond its farthest extension. The first is of two kinds: 

 that produced while the icecap was growing and advancing, and 

 that left as it retreated or melted away. Of course it is not yet 

 certain whether the land slid in under a permanent polar icecap, 

 whether the icecap crept south over the land, or whether it 

 developed in situ. There was obviously a southward movement 

 of ice, but this need not have been a gradually expanding cap 



84 



