h;-n 



PHYSICAL GEOGEAPHY. 



f^^t ndcns out into tlic Llano Estacado (staked plains) of Nortliern 

 j^j[qj Cexas, and tlie yast plain — the Madre Plateau — which 

 gjjjj^jccupies Southern !New Mexico. 



•^^^^ A few figureSj representing average elcA^ations only, may 



ye desirable. The staked plains of Texas average 3,500 



)et; the Madre Plateau ahout 4,000. Eising from these, 



F 



i^jQd passing northwards, the "Summit Plateau" attains an 

 f iurerage elevation of 7,000 feet in ^N'orthern l^Tew Mexico, of 

 . i^^j'om 8,000 to 9,000 feet in Colorado, 7,000 in Wyoming, and 

 . ^^ oni 5,000 to 2,000 in Montana, whence it passes into 



ritish territory. 



. ^g The country lying hetwecn the highest portions of the 



|..[^g Summit Plateau'' in Colorado and the Mississippi ascends 



. ^gT more rapidly than the adjoining country south of it, which 



.jj^gDCS not ultimately attain in New Mexico so great an 



^ . iu.evation j while to the north of Nebraska, Kansas, and 



-olorado, the country has not only a still lower elevation to 



a' 'ach on the Summit Plateau in Montana, but (consequent 



a 



;,pon the north-westerly dii-ection of that central line of 

 laximum elevation) has a far longer distance in which to 



,3ach it. Wo therefore actually find what theoretically we 

 ^ ' lould expect — that the largest river in the continent flows 

 ^Ij^irough this district. 



rfd»8^^The Missouri at Port Benton, the head of steamboat 

 »»f'ii^vigation, is 2,500 miles by water from its mouth, and 3,737 

 Hflosti^pm tide water, and yet at the 111th meridian (South Park 

 ]jjBi*ing on the 106th) it is only 3,000 feet above the sea. 



le cause is obvious. The streams of the high lands of 



j^tcp^^estem Montana, where the springs do not average more 



1**^ m 6,000 feet, pass northwards around the most lofty part of 



'^ *Jl continent, and do not commence a southward course towards 



j4lt^ Gulf until 700 miles separate them from their western 



# 



r 



