MOGOLLON SYSTEM—ELEVATION AND STRUCTURE. 
165 
pentine of that range, and in the conglomerates of the Calitro and Santa Catarina. Veins of 
argentiferous lead ore might, if looked for, he found in Chiricahui, since it exists in the same 
rock east. 
During the series of elevations which finally uplifted this entire range to its present altitude, 
the upheaving force must have been exerted even upon the southern portion of the range, 
raising the table land of northern Sonora and Chiricahui to so great a height. This strain may 
have produced a fissure from east to west, or cracked, and perhaps depressed, the strata along 
parallel 33°, and thus enabled the Gila to take that as its permanent course. Some such catas¬ 
trophe must have occurred ; for it is scarcely probable that the river, unaided, could have cut 
through such lofty hills and hard rock as it appears to have done in its passage through these 
mountains, running, as it does, at right angles to the strike of the ranges. 
The valley east of the San Francisco river separates the Pinaleno mountains from the western 
ranges of the Mogollon and Sierra Blanca hills. The table land on which these ranges are 
placed varies from 3,000 to 4,000 feet, and the summits of the highest hills reach 6,000 and 
6,400 feet above the sea level. Mount Graham is the loftiest mountain in the entire system. 
MOGOLLON SYSTEM. 
The Mogollon mountains lie north of the Gila river, and east of the San Francisco, one of its 
tributaries. In this region, by many heads, the Gila rises, and from it it derives five-sixths of 
its whole volume of water. They are a lofty series of mountain ranges, between 108° and 110° 
west longitude, and 33° and 35° north latitude, lying north and east of the Pinaleno moun¬ 
tains, with which they have been confounded. But the different trend of the ranges show that 
these two series of mountains are distinct from each other, the dividing line of which upon the 
Gila is between the rivers San Carlos and San Francisco. The Pinaleno ranges run more 
north and south, never exceeding N. 45° W, while the Mogollon ranges run more east and 
west, and have an average trend of N. 65° W. and S. 65° E., or nearly twenty degrees more 
east and west than the former range.* 
Little of the country embraced within these limits is known to white men ; it is the country 
of the Gila Apaches, where they have their strongholds and their lands of cultivation. 
The Sierra Blanca range, which lies the most eastward, is very lofty, and, viewed from the 
north, appears to have an east and west strike. 
The rocks which enter into the composition of this great mass of mountain, are whitish 
felspar granite, and amphibolic granite, metamorphic quartz, old red sandstone, and, according 
to Mr. Marcou, magnesian grits of the carboniferous system, magnesian limestone, and trias 
beds. 
They are a very lofty range of mountains, reaching to an elevation of 10,000 feet in many of 
their summits. Snow is seen upon these for many months of the year, the meltings of which 
give rise to the Gila, and form the Salinas, which joins the Gila lower down. 
The snow-capped region, thus yielding water during the summer months, is the cause of the 
fertility of the mountain vallies in the range, producing fine grass and corn to the Indians. 
The ranges of hills which lie between the Santa Catarina range and Fort Yuma, and round 
which the Gila travels in its course westward, are of lesser importance than those enumerated. 
With the exception of the Sierra Estrella west of the Pimas plains, and east of the jornada, 
* Mr. Marcou, in Ms geological chart and sketch, (report to the Geological Society of France,) describes the Mogollon 
mountains as extending from longitude 108° to 114° W., and throughout having a dip of N. 60° W. This is erroneous; 
it makes the Mogollon mountains occupy a district much larger than it actually does. 
