INTRODUCTION. 



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forms tlie diYitle,* can be crossed at an elevation of 1,158 feet, , 

 on the same parallel as the sontliern shore of Lake Superior. 

 From the head-waters of the Mississippi northward, the land 

 falls gradually towards Lake Winnipeg in British territory. 

 Thus the rise of the continentj north and south, only just 



exceeds 1,000 feet. 



Passing westtvard from the Mississippi^ and disregarding 

 mountains altogether for the present, the elevation of the 

 continent gradually increases, until it attains its highest 

 level at South ParJc^ about the centre of Colorado. 

 If we compare the rise and fall of the continent on 

 all sides to two saddles, placed pommel to pommel, the 

 pommels will represent South Park, the highest part of the 

 median line of maximum elevation, while the prominence 

 sloping downwards from each pommel, and disappearing at the 



back of each saddle, will well illustrate the course of the 

 " Summit Plateau/' For this ^^ Summit Plateau,'' if it may 

 be so called, diverges from its greatest elevation in a north- ^ 

 westerly direction, to form the less elevated watershed in 

 Montana, between the heads of the Missouri and Columbia 

 rivers; while to the southward it gradually falls also, and 



* The term ''divide," used as a substantive, may be objected to, on tlie 

 ground that it is not English,- This I grant; but as it is in common use 

 throughout North America, is often to be heard at the Meetings of the Eoyal 

 Geographical Society, and" is frequently so printed in their IJeports, I have 

 preferred to use it generally instead of its sjTionym " water-parting," because, 

 in such compound expressions as ** secondary water-parting " or ** continental 

 water-parting, ** secondary divide " or '* continental divide," sounds shorter and 

 crisper. *' Di^-iding-ridge," of course, is only applicable when a mountain range 

 forms the divide. 



It may be well at the outset to give the following definitions : — 



A watershed is the slope between a water-parting, or divide, and a watercourse. 



A divide is the boundary-line between continruous basins and watersheds. 



united 



first, second, third order, &c., constitutes a hasin. 

 {See " Physical Geography," from the Frencl 

 Captain Lendy, F.G.S.) 



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Th. Lavallee. Edited^ by 





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