Explorations and Surveys for the Pacific Railroad. 71 



the deception arising from the overlapping of the side spurs to 

 chains, the general direction of which is north and south. 



The "triangular space" lying between the Eio Grande, Gila, 

 and Colorado, is everywhere, so far as known, exceedingly 

 mountainous ; the ranges, such as the Mogollon and San Fran- 

 cisco mountains, having a general northwest direction. Too 

 broad an interval exists between the explorations of Lieutenant 

 "Whipple and those of Captain Gunnison, to enable us to speak 

 with certainty of their relation to the systems already alluded to. 



In portions of the mountain region, the waters find no outlet 

 to the sea, but drain into lakes and ponds, or sinks, carrying 

 with them all the impurities of the basins to which they belong, 

 and are there uniformly brackish or very salt. Prominent ex- 

 amples of this are the Salinas Basin, of New Mexico, and the 

 Great Salt Lake Basin in Utah. 



From most portions of this interior mountain belt, the waters 

 have been able to force their barriers and escape to the ocean. 

 The valleys thus drained are, those of the southern tributaries 

 of the Upper Missouri, that of the North Fork of the Platte, 

 and its tributary the Sweet Water, between the first and second 

 systems ; that of the Upper Eio Grande del Norte, in the first 

 system ; that of the Great Colorado of the West and its tributa- 

 ries, between the first and second systems ; those of the waters 

 of the Bay of San Francisco and of the Klamath river, in the 

 third system ; and that of the Columbia river and its tributaries, 

 between the second and third systems. Some of these streams, 

 as well as others in the enclosed basins, have, in places, worn for 

 themselves through the solid rock, the most stupendous chasms 

 or canons, often 2,000 feet in vertical height, many of which it 

 is impossible to follow or to cross. 



The position of this belt of mountain region, stretching from 

 north to south, gives rise to a peculiarity of climate and soil. 

 Fertility depends principally upon the degree of temperature 

 and amount of moisture, both of which are much affected by in- 

 crease of elevation ; and the latter also depends on the direction 

 of the wind. The upper or return current of the trade-wind, 

 flowing backward towards the northeast, gives a prevalence of 

 westerly winds in the north temperate zone, which tends to 

 spread the moisture from the Pacific over the western portion of 

 our continent. These winds, however, ascending the western 

 slope of the mountain ridges, are deprived of their moisture by 

 the diminished temperature of the increased elevation; and 

 hence it is that the plains and valleys on the eastern side of the 

 ridges are generally parched and barren, and that the mountain 

 system, as a whole, presenting, as it were, a screen against the 

 moisture with which the winds from the west come laden, has 

 for its eastern margin a sterile belt, which probably extends 



