20 POOLE'S SURVEY FROM SAN DIEGO TO FORT YUMA. 



ci^rves, and the steep grades confined to the tangents or straight line portions. A careful exam- 

 ination of the side hills of this caiion demonstrated that, in general, no material increase in the 

 cost of construction would ensue from placing the road at a considerahle elevation ahove the 

 line actually surveyed ; indeed, the safety of the superstructure would seem to compel such a 

 location, the district heing 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 banks. The additional expense 

 of the few bridges or embankments that may be 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. 



YALLEY 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 jjoint 

 in the rear of the Mission, about 90 feet higher than the level of the valley, ofi'ering 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 be easily modified, so as to secure a level track for some distance on each side the 

 station. 



SUMMIT OP 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 be 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 JOSfi AND WARNER'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 tlie 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 



