FROM VALLE DEL SAUZ TO MOUTH OF RIO SAN PEDRO. 
23 
is somewhat broken, and the slopes of the opposite sides meet, forming broad and smooth 
summits. That selected is about four and one-half miles south of the Sugar Loaf, and has an 
altitude above the basin bottom on the east of 391.3 feet, and above the bottom of the Yalle 
del Sauz of 172.5 feet. The approaches to this summit are of such a character as to permit a 
decrease of gradients by an increase of distance. 
SECTION 3. 
Second Division. —From Valle del Sauz to mouth of Rio San Pedro .—The Yalle del Sauz 
and valley of the San Pedro are tributary valleys of the Gila, whose axes are nearly parallel, 
and distant about fifty-five miles. They embrace an interior plain and valley district which 
is separated from the two bounding valleys by divides, whose peaks and ridges are as lofty 
and imposing as the passes are inviting and easy of transit. This division affords a striking 
illustration of the parallelism of the ridges of this interior region, and their bearings upon 
the directions of the valleys and their drainage. The Yalle del Sauz trends off to the northwest, 
a broad and open valley, receiving in its course the valley of the Gila as it opens out 
from the northeast, playing rather the part of tributary than main valley, since it imme¬ 
diately assumes the direction of the Yalle del Sauz, and preserves it for about sixty miles. 
Here the Gila again changes its course to the southwest, and, piercing the Pinaleno mountains, 
opens from a rugged canon into the valley of the San Pedro, and trends off twenty-one miles in 
the direction of its axis, where, encountering another and the last obstacle, it again runs to the 
west and enters a canon leading through to a plain, affording a free flow to the Colorado of 
California. The western limit of the Yalle del Sauz is made up of two mountain masses— 
Mounts Graham and Chiricahui—the grandest and most imposing yet encountered, whose axes 
topographically form a continuous line, with an intervening gap or break of about eight miles, 
lying directly in our course westward. That on the north of this gap, Mount Graham, looms 
up, solid and massive, with an apparently continuous outline, trending off to the northwestward 
until lost below the horizon. This continuous range is called Pinaleno mountains. 
The Chiricahui on the south is not so compact, but broken into radiating ridges and spurs, 
whose crests are serrated and pinnacled, rendering the mass easily distinguishable at great 
distances. Near the northern end of this mountain two of these pinnacles stand conspicuously 
above the profile of the surrounding height, and, from their great uniformity in figure and 
dimension, are called the Dos Cabezas (Two Heads.) These mountains rise abruptly from the 
slopes of the surrounding valleys, and are generally rugged, bare, and destitute of timber, a 
small growth of dwarfish oak, wild cherry, ash, and walnut, (black,) and cedars, being found in 
the valleys and canons. On the right bank of the San Pedro trends off a ridge or chain of 
ridges, which, by their interlocking, form an apparently continuous divide between the San 
Pedro valley and the interior plain district, of the Play a de los Pimas. This chain, the 
Calitro* mountains, although secondary to the one preceding, in point of elevation and extent, 
nevertheless plays a conspicuous part in the physical geography of the narrow belt or zone of 
our continent contiguous to the thirty-second parallel route, it being the western limit of the 
great central plateau which extends eastward to the sources of the Colorado of Texas, 
embracing an area of about ten degrees of longitude, where the mean elevation does not exceed 
5,000 feet. 
The area embraced by these two mountain chains, is made up of two distinct features, basin 
* This name was obtained from the oldest inhabitants of Tuczon, and is, probably, a corruption of calizo, (lime,) there 
being an abundance of this material there.—A. H. C. 
