PHYSICAL GEOGEAPHY. 



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a 



rraiici5C0),LS of general elevation^ mdependent ranges, varying con- 

 mreads ou&erably in direction, height, and extent, have been piled 

 moimtainit in great apparent confusion, while here and there some 

 3 best aiKf y lofty peaks mark the probable centre of volcanic action 



special localities. 



lie^The explorations made nnder the auspices of the American 



andtvemment, and embodied in the bulky volumes of the 



fftli of tie cific Eailway Eeports, have been followed up by sur\^eys 



h\^ of thed explorations, undertaken by private companies and others, 



.nctrate thf that the knowledge acquired from these many sources has, 



f ^outlienJ^^^^'^j disclosed a certain regularity of design throughout 



fXortliPi^ entire " Summit Plateau" system, which greatly simpKfies 



5iiortli^ar(i.i topography. 



K.hreen^'i' ^^ ^^^ question, Where is the central range of the Eocky 

 ., j^lvtountains ? I confidently answer, Kowhere ! There is no 

 , , j^cte:»iitinuous central chain whatever. It appears to me, on the 



0^ i . . . 



;>ntrary, from my own observations, and from diligently 



J flfiamimng the explorations of others, that the so-called Eocky 



^ rfiloTiiitain system, from the northern boundary of the United 



^ »tates to theii' southern termination, consists usually of two 



^' . j-trfiif-^^^^^ ^^ mountain ranges, occupying the eastern and western 



'dges of the ^^ Summit Plateau," and separating it from the 

 i^laias on either side. 



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■^^ 



'^ ^^ ^ 3; These eastern and western chains communicate by means 

 r • \ . jf transverse ridges at irregular distances, thus cutting up the 



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Summit Plateau " lying between them into a succession of 



"^ "^^ -solated plaius or " parks " of great elevation 



^uli) The word "park," in Eocky Mountain phi'aseology, has a 



tefO^^ . .pecific signification, and is used exclusively to designate those 



bo 



)^ ofty, well-watered plains, or prairies, to be found all along the 



¥^ '^ Summit Plateau," shut in on all sides by mountains. 



^^^^ ' Secondary ranges radiate froin the primary chains, and jut 



