BULLETI]Sr 820, U. S. DEPARTMENT OF AGRICULTURE. 



origin developed by the weathering of the underlying rock. This is 

 the "Great Laurentian Shield," which comprises over 50 per cent of 

 the area of Canada and extends from the northwest arm of the Lake of 

 the Woods, northwestv/ard and northward to the mouth of the Mac- 



kenzie River, the Arctic Ocean, and the mouth of the Winnipeg River, 

 and eastward through Ontario, Quebec, and Labrador, (See j&g. 1.) 

 Lakes, rivers, and swamps alternate with low hills and plateaus, which 

 show a remarkably even sky line. The network of waterways extends 

 throughout the region. The soil is found mostly along stream 

 valleys (alluvial), on the southern exposures of ridges (glacial sands 



