20 
POOLE’S SURVEY FEOM SAN DIEGO TO FOET YUMA. 
curves, and the steep grades confined to the tangents or straight line portions. A careful exam¬ 
ination of the side hills of this canon demonstrated that, in general, no material increase in the 
cost of construction would ensue from placing the road at a considerable elevation above the 
line actually surveyed ; indeed, the safety of the superstructure would seem to compel such a 
location, the district being subject to heavy freshets during the rainy season, and the bed of the 
stream indicates the occurrence of immense floods, whose volume is so great as to leave accumu¬ 
lations of drift-wood in the topmost branches of high trees on its hanks. The additional expense 
of the few bridges or embankments that may he required in passing the outlets of gulches and 
ravines intersected by the line, will not much exceed the cost of protecting a lower track from 
the consequences of these torrents. 
V ALLEY OF SANTA ISABEL. 
From the entrance of this valley to the rancho, or Old Mission of Santa Isabel, the line passes 
over the flat meadow or bottom land at a nearly level grade for 2.21 miles ; round the valley 
on all sides are gently undulating hills, covered with oak trees, the soil being gravelly and 
apparently favorable for excavation. The valley is supplied with unfailing springs and streams 
of the purest water, whose contents may be collected by means of reservoirs to supply a water 
station in any desired quantity. Approaching the Old Mission it is proposed to elevate the 
track above the level of the valley, by deflecting the line to the right, and carrying it along the 
side hill, in order to gain a higher elevation with which to pass the adjacent summit. A point 
in the rear of the Mission, about 90 feet higher than the level of the valley, offering an eligible 
position for a station, it is assumed as the starting place for the grade over the summit. The 
ascent to this place from the entrance of the valley is at the rate of 64.72 feet per mile. This 
grade can he easily modified, so as to secure a level track for some distance on each side the 
station. 
SUMMIT OF SANTA ISABEL. 
Passing along the foot hills of this valley a rising ground, hemmed in by high hills, appears 
in front, over which now runs the main road to Fort Yuma. This road is intersected by the 
line at about a mile from the Mission, and the line is identical with it through the pass, and 
nearly to the foot of the hill in the valley of San Jose. At the summit no impediment to exca¬ 
vation is apparent on the surface, and it is believed that a cut of 80 or 100 feet in depth can he 
made without striking solid rock. Assuming a cut of 80 feet, the resulting grade of the line 
from the Santa Isabel station will he 100 feet per mile for 2.33 miles. Oak timber in great 
abundance is growing in the immediate vicinity of the line, and within six miles from San 
Isabel are vast forests of pine of superior quality, covering all the elevated lands east of this 
part of the route. 
SAN JOSE AND WAKNER’S RANCHO. 
Leaving the summit to descend to the valley of San Jose, we find the grade of the natural 
surface to be about 175 feet per mile for upwards of 3 miles. This can be decreased by keeping 
to the right and following around the sides of the neighboring hills. This may tend rather 
to reduce than increase the distance, unless the curvatures should prove considerable. A grade 
of 92 feet for 3^ miles from the summit would reach a point 195.49 feet above the level of the 
