24 FROM THE PIMAS VILLAGES TO THE KIO GRANDE. 



and valley ; but these being, in this case, so intimately connected, we will give the whole 

 district the name of the most prominent, the Playa de los Pimas. The term playa is given to 

 the beds of these small basins or depressions, which receive the drainage from the surrounding 

 slopes. During the season of rain, the surface waters are collected and spread over a broad 

 level area, soon to be absorbed and evaporated, leaving the beds smooth, and to be baked hard 

 by the mid-day sun of the dry season. These playas are often called lagunos, dry lakes, salt 

 lakes, &c., dei:)ending solely upon the time or season of the traveller's visit. 



The Playa de los Pimas, the largest encountered during our examinations, is immediately to 

 the west of the Dos Cabezas, or northern end of the Chiricahtii mountains, and covers an area 

 of about sixty square miles. Its surface was, when crossed February 28, 1854, and also 

 July 30, 1855, hard and smooth, and apparently as level as a frozen lake. In fact, the effect 

 in crossing, excejjting in j^oint of temperature, was very analogous to that exi^erienced in 

 crossing a broad, smooth field of ice. Not a particle of vegetation is found upon its surface, 

 which is entirely free from dust, and so hard that our mules and heavily laden wagons scarcely 

 made an impression upon it. It is bounded by smooth and grassy plains, sloping back to the 

 bases of the mountains. 



To the northwest of the Playa the plain slopes up to a scarcely perceptible summit, beyond 

 which the waters between Mount Graham and the Calitro Mountains, forming the Aravaypa 

 Creek, are drawn off thirty miles parallel to these mountains, and then meeting an obstacle 

 to its continuous progress to the Gila, turns westward, and by a short canon through the Calitro 

 Mountains enters the valley of the San Pedro, twelve miles above its mouth, presenting thus, in 

 a small scale, the same striking features as the Upper Gila. 



The Eio San Pedro, a tributary of the Gila, the western limit of the 2d section, heads in 

 the plateau in which the Yaqui and other rivers of the Gulf of California take their origin, 

 and trends off one hundred and twenty-six miles to the northwest, draining a valley or trough 

 lying between parallel ranges, the average width of which is about fifteen miles, the alluvial 

 bottom being about three-quarters of a mile wide. 



Col. Cooke, in 1846, struck this stream near its source, and followed down its valley, with a 

 train of wagons, fifty-five miles to the Tres Alamos, and there turned westward, following a 

 trail leading through a break in the mountains to Tucson. 



At the Tres Alamos, the valley is open^ broad, and smooth, bounded by low terraces, which 

 slope back to the bases of the mountains. The valley continues open, down to a point opposite 

 the southern end of the Santa Catarina Mountains, (Colorado Peak,) where the foot .spurs of this 

 mountain bluff down, meeting the terraces on the right bank from the Calitro Mountain, and 

 changing the direction of the valley for a short distance, reduces it to a gorge. Below this 

 gorge, the valley alternately widens and narrows to its junction with the Gila, leaving beautiful 

 oval meadows, separated by short stretches of bottom land, which have been narrowed down 

 to a few hundred yards by the bluffs of the impinging spurs. 



These meadows are grassy and inviting, and bounded by terraces, the foot slopes of the ad- 

 jacent ridges, ranging from twenty to one hundred feet in altitude. These terraces are sparsely 

 covered with a growth of grama grass, cereus, and larrea, and the surfaces are generally 

 smooth, forming, in extension, continuous and uniform slopes, but at the same time are much 

 cut up by deep drains and washes, ramifying like the woody fibres of a leaf. 



The valley bottom is generally smooth and open, with the stream bed curving through it, 

 sometimes a few inches, and at others as much as fifteen feet below the surface of the meadow. 



