THE CENTRAL REGION OF NORTH AMERICA. 



615 



origin, with, however, a good deal of the 

 usual white limestone and a slight admix- 

 ture of the quartzite drift. The whole of 

 the Coteau-belt is characterized by the 

 absence of drainage- valleys ; and in con- 

 sequence its pools and lakes are often 

 charged with salts, of which sulphates of 

 soda and magnesia are the most abundant. 

 The saline lakes frequently dry up com- 

 pletely towards the end of the summer, 

 and present wide expanses of white efflo- 

 rescent crystals, which contrast in colour 

 with the crimson Salicornia with which 

 they are often fringed. 



Taking the difference of level between 

 the last Tertiary rocks seen near the 

 eastern base of the Coteau, and those first 

 found on its western side, a distance of 

 about 70 miles, we find a rise of 600 feet. 

 The slope of the surface of the underlying 

 rocks is therefore, assuming it to be uni- 

 form, a little less than 100 feet per mile. 

 On and against this gently inclined plane 

 the immense drift deposits of the Coteau 

 hills are piled. 



The average elevation of the Coteau 

 above the sea, near the forty-ninth parallel, 

 is about 2000 feet ; and few of the hills 

 rise more than 100 feet above the general 

 level. 



Between the south-western side of the 

 Coteau belt and the Tertiary plateau is a 

 very interesting region with characters of 

 its own. Wide and deep valleys with sys- 

 tems of tributary coulees have been cut in 

 the soft rocks of the northern foot of 

 the plateau, some of which have small 

 streams still flowing in them fed by its 

 drainage ; but for the most part they are 

 dry, or occupied by chains of small saline 

 lakes which dry up early in the summer. 

 Some large and deep saline lakes also 

 exist which do not disappear even late in 

 the autumn. They have a winding, river- 

 like form, and fill steep-sided vallej^s. These 

 great old valleys have now no outlet ; they 

 are evidently of preglacial age, and have 

 formed a part of the former sculpture of 

 the country. The heaping of the great 

 mass of debris of the Coteau against the 



