PHYSICAL GEOGEAPIIY. lui 



Grama grass; and although much of it is wild and 



. ,p.^n, cut up by ravines and impassable barriers, still the 



2:ns of mineral wealth evervwhcre abound, and -nrcdict a 



if 



t i! 



^s section of country, 



; Gnlf of Mexico lias no great obstacle 



bar its way between the Texan coast and these regions, and 



cause its precipitation before arriving at them; for the 



Summit Plateau'' in this latitude has sloped away, and the 



ocky Mountain chains have ceased to be conspicuous^ so 



hut the rainfall about the mountains of Central Arizona is far 



4 



jTcater than the trayellers' who have passed north, or, as is 

 nore usually the case, south of them^ in the more level though 



arid districts, are aware of, 



B next belt of mountain ranges, also trending north-west 

 md south-east, is that which has the Aztec Mountains, Bill 

 Williams Mountain, and perhaps the San Francisco peaks, to 

 *'%iark its northern extremity. It passes obliquely across 

 i: Arizona, cresting the San Francisco Plateau, forming the 



)rth and south of the Eio Gila; the 



T 



'C^hirieahui Mountains, their continuation ; the Sierra Calitro 



irina, parallel ranges: then, crossing 



r ■ i 



» 



r* 



Sierra de Santa Cat 



• i^' 



the boundary line into Mexico, the mountain sources 



4 l^an Pedro and Santa Cruz riyers form part ot the same belt 



.of upheaval. At last it is merged into the Sierra Madre, 

 ' %liich caps the plateau of Mexico. If the Sierra Madi-e, or 



^ i main mountain chain of Mexico proper, be a continuation of 

 any northerly chain, it is of that which I have just mentioned, 



,.!*and not, as is commonly but erroneously supposed, of the 

 Ptocky Mountains, which undoubtedly lose themselves at least 

 2° to the north-east in the broad plateau of Xew Mexico, 

 commonly known as the Plateau of the Sierra Macbe. 



When a range of mountains forms the main continental 





