712 C. R. KEYES MID-CO'NTlNENTAL EOLATION 



Many of the desert ranges display another peculiarity. Tlie stream- 

 ways do not always continue directly out on the adjoining plain nntil 

 their sporadic waters sink ont of sight. On one side of the range, and 

 sometimes on both sides, these drainagew^ays, soon after leaving their 

 canyon mouths, enter a master stream, the course of which is in a direc- 

 tion parallel to the mountain axis. When they appear torrential waters 

 are not carried forward as might be expected, but are diverted toward 

 one end of the range or the other, there to enter a thro-ugh-flowing river. 

 In illustration, the Sandia and Manzano ranges, east of Albuquerque, 

 New Mexico, may be cited; not a drop of water falling on these moun- 

 tains reaches the Estancia plains to the eastward. In the lofty Sierra 

 de los Caballos, which forms the western border of the broad Jornada del 

 Muerto, in southern 'New Mexico, canyons at the foot of the eastern 

 slope do not permit a single waterway to drain out onto that vast plain. 

 In the Funeral range, in N"evada, the same conditions prevail. Many 

 more instances might be mentioned. The principle involved is especially 

 applicable to the Great Plains along the Eocky Mountain front. 



At the base of the Cordillera, in Colorado, the railroads traverse the 

 entire breadth of the State in a deep north and south valley. The ridge 

 formed on the east side of this valley is not a range of foothills genet- 

 ically related to the mountains, but is merely the western margin of the 

 Great Plains surface. Within the limits of Colorado this ridge is broken 

 by streams only at two points. The Platte and the Arkansas rivers are 

 the only streams rising in the Eocky Mountains that pass into the Plains 

 region. This fact is still more notew^orthy when it is remembered that 

 in all the great distance between the Canadian and Mexican boundaries 

 the waters of only five rivers whose headwaters are in the Eockies become 

 streams of the Great Plains. Contrary to general opinion, the Cordil- 

 leran-born streams, with the five exceptions mentioned, debouch not upon 

 the Plains. 



No matter how favorable otherwise are the conditions in the Great 

 plains region for extensive stream aggradation, the meager number of 

 rivers actually present are manifestly so vastly inadequate for the work 

 that there arises at once the query as to how much of the aggradation 

 hypothesis could have been based upon direct observation. Evidences of 

 unquestionable river action of a constructive character appear only in 

 the immediate vicinity of the few through-flowing streams already men- 

 tioned. Nowhere in the country between these rivers have I noted any 

 indications whatever of deposits that could possibly be ascribed to fluvia- 

 tile influences. 



