EVIDENCE OF LIMITED RAINFALL ON THE PLATEAU. 
151 
silicious sand. From the character of the vegetation on the slope, it is evident hut little water 
is retained there, and no creek carries its bed sufficiently far to deliver its waters into the Sauz 
stream. The rain water absorbed into the soil probably finds its way to the lower level of the 
valley near the river bed, and may go to form the water pools existing there in dry seasons. 
Although no rock was observed here in place overlying the limestone, yet the depth of 
detritus and gravel on the upper edge of the plain leads to the suspicion that a sandstone rock 
is the immediate basis rock; the reddish silicious sand also presupposes that it is a reddish 
sandstone, such as is found further east. 
Looking hack at Chiricahui from the Sauz brook it appears a much larger range than when 
seen from the playa. The eastern and southern prolongation of the mountain is only visible 
from the Sauz valley, where it appears to run 30 miles south of the canon. The highest peaks 
of the mountain also lie to the south of the Puerto, and attain an elevation of 6,000 feet above 
the sea, or 2,000 feet over the plain on either side. At such an elevation this great mass of 
rock must attract the rain clouds of summer and receive a large supply of water ; from Septem¬ 
ber to April its summits must he frequently capped with snow, thus increasing the water supply. 
Still, it may he asked, what becomes of this water ? is it all confined within the valleys of the 
range? The arroyo beds, which are numerous and some of them deep, leading from the flanks 
of the hill, flow one, two, or it may he even three miles into the plain, but, sooner or later, 
they ultimately lose themselves in the detritus of the valley; and of the few arroyos which drain 
out from the interior of the mountain into the external plain, not one of them flows permanently. 
There is not, in fact, comprised within the whole mountain region or its confines, one single 
permanently flowing stream. The stream beds show that occasional flows of water occur from 
excessive rain or from unusual thaws of snow, and that from their sudden rise the waters exert 
a great force in scooping out a channel; hut this only exists for, at most, a few weeks in the 
year, and thenceforth diminish, so that for three-fourths of the year they are represented by dry 
beds. From the apparent condition of the surface, we must conclude, notwithstanding the lofty 
elevation of the basal plain and the mountain ranges, that hut a small amount of rain falls in 
the year, and that the solar evaporation must he very nearly equal to that rain fall, whatever 
its amount; for, if not, the plains would become water soaked from having no good surface 
drainage, and would produce a varied and abundant vegetation. 
