TERMINAL M0BAWE8. 



219 



color with the crimson Salicomia with 

 which they are often fringed. 



Taking the difference of level between 

 the last Tertiary rocks seen near the east- 

 ern base of the cotean aud those first found 

 on its western side, a distance of about sev- 

 enty miles, we find a rise of six hundred 

 feet. The slope of the surface of the under- 

 lying rock is, therefore, assuming it to be 

 uniform, but little more than four feet 

 per mile. On and against this gently in- 

 clined 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 2,000 feet ; and few of the hills rise 

 more than one hundred feet above the gen- 

 eral level. 



Between the southwestern 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 oc- 

 cupied 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 valleys. These great old 

 valleys have now no outlet ; they are evi- 

 dently of preglacial age, and have formed 

 a part of the former sculpture of the coun- 

 try. The heaping of the great mass of 

 debris of the coteau against the foot of the 

 Tertiary plateau has blocked them up and 



II 111 



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