8 VEGETATION OF A DESERT MOUNTAIN RANGE. 
The highest elevations lie between Mount Lemmon (9,150 feet, 
2,790 m.) and Green Mountain (7,900 feet, 2,410 m.), which are only 
7 miles (11 km.) apart. Samaniego Ridge and Oracle Ridge extend 
northward from the vicinity of Mount Lemmon, falling rapidly in 
elevation and terminating in the high plain which lies in the direction 
of the Tortilla Mountains. A very rugged ridge extends southwest- 
ward from Mount Lemmon and terminates in Pusch Ridge. To the 
south of the main ridge an extensive elongated drainage basin has been 
developed which lies parallel to the south face of the range and finds 
its outlet through Sabino Cafion. Several important streams drain the 
south slopes of the main ridge and are tributary to Sabino Cafion. To 
the east of Sabino two important drainages—Bear Cajion and Soldier 
Caiion—drain the eastern end of the main ridge in the vicinity of Green 
Mountain, and west of Sabino are Pedregosa, Ventana, Pima, and other 
cafions which rise in the rugged southwestern portion of the mountain. 
All of these streams flow into the Rillito, a tributary of the Santa Cruz 
which also drains a portion of El Rincon range. The north face of the 
main ridge between Oracle and Samaniego ridges is drained by the 
Cafiada del Oro, which flows at first north, then west, and finally south- 
west, emptying into the Santa Cruz. On the northeast slopes of the 
range the topography is relatively simple, the high elevations falling 
away rapidly in the direction of the San Pedro River. A large number 
of minor streams drain this region and give to the San Pedro perhaps 
less than one-fourth of the total run-off of the mountains. 
The main drainageway of Sabino Cajion is the only one in the Santa 
Catalinas which possesses a constant flow of water, which is due both 
to the great extent of its cachment basin and to the fact that it has 
its source on the north slopes of Mount Lemmon in the heaviest body 
of timber on the mountain. In the Cafiada del Oro, in Bear and Soldier 
Cajions, as well as in a few of the larger cafions of the north slopes, 
water may be found at all times of the year in certain localities where 
the local configuration of the valley or the occurrence of resistant dikes 
of rock forces the underflow to the surface. During the rainy seasons 
water may, of course, be found in any of the large drainageways. The 
heavy local showers of summer often convert even the smallest stream- 
ways into rushing torrents for a few hours. 
The small size of the Santa Catalinas together with their elevation 
gives a steep gradient to all of the major streams. The main stream 
of Sabino Cajion falls from 7,700 feet at Webber’s Cabin to 3,700 feet 
at the west end of Sabino Basin, a distance of 6 miles, or a gradient 
of fall of 667 feet per mile. From the west end of the Basin to its 
emergence onto the desert this stream falls only 1,000 feet in a distance 
of 5 miles. The Cajiada del Oro falls at a rate of 494 feet to the mile 
from its source, just west of Mount Lemmon, to the zonfluence of its 
main tributary from the west slopes of the Oracle Ridge, and at the 
