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



indication of water on this portion of tlie line. It disappears a few rods below the border of 

 the marsh, and the sandy creek again becomes dry. 



The slopes of this valley offer every facility for the location of the road, being broad inclined 

 planes, composed of coarse gravel and sand, derived from the washing and wearing down of 

 the mountain sides. Over the long, straight portions of this line a grade of 200 feet to a mile 

 might with safety be adopted, though that of the whole line, from the station at Oak Grove to 

 the village, a distance of 8.92 miles, is fixed at 106 feet, arriving on the slope behind the 

 Indian huts at a point 22 feet above the level of the wagon road. 



Half a mile before reaching the village water again appears in the form of springs. It is 

 considered inferior in quality, and has a peculiar taste, due to the presence of alkaline or other 

 salts. Vegetation here consists only of some varieties of cactus, sage, and a few samples of low 

 inesquite and stunted cedar bushes. Far up the valley of " Volcan," which enters the valley 

 nearly opposite this point, may be seen, however, dark forests of pine timber crowning the 

 hill tops. These are ten miles off, but transportation to this point is not difficult. 



From the Indian village two routes were surveyed to the open plane of the desert. The first 

 was by way of the wagon road, as at present travelled, and the other through a canon which 

 conducts the waters of San Felipe into an adjoining valley leading directly to the desert. 



The results obtained by the former do not vary materially from those obtained by Lieut, 

 Williamson in his examination of the same ground in 1853;, though they are not, of course, 

 identical with them in every respect, owing to the different methods of observation pursued. 

 An inspection of the tables appended to this report will serve to show, when compared with the 

 data furnished by the survey of that officer, the slight difference between the measurements of 

 altitudes by the barometer and those of the spirit level. 



FROM SAN FELIPE TO THE COLORADO RIVER, BY WAY OF THE "WAGON ROAD. 



Eeports of this route having been frequently made by officers in the service of the govern- 

 ment, it will be only necessary to briefly allude to its characteristic features. The face of the 

 country throughout this distance of 125 miles may be described as a desert, though tlie name is 

 generally only ajjplied to the level portion of the route. For forty miles before reaching the 

 open expanse of the desert the road traverses sandy canons and sterile basins, bounded on all 

 sides by bare and rocky mountains, without enough of earth to cover their nakedness. Water 

 is found only at distant points, and the absence of this element, combined with the intense 

 heat, gives to the landscape a desolate and forbidding aspect. 



From San Felipe the road commences a gentle ascent, and leaves the valley at a distance of 

 5.59 miles, at a grade of 36.8 feet per mile, passing a narrow ridge 50 feet in height, requiring 

 a cut through rock of 450 feet in length. Crossing a small basin at a grade of 30.5 feet, we 

 come to the entrance of a caiion at 2.46 miles. This caiion, which is extremely crooked, has 

 a grade of 189.16 feet per mile for 1.42 miles, which, by resorting to the side hills, may be 

 reduced to 100, making it necessary to cut and fill a series of rocky spurs and narrow ravines. 

 From the foot of this caiion to the puerto or pass, beyond which there is no obstruction, the 

 natural surface has a grade of 96.5 feet a mile, which would be increased to about 100 if the 

 side hill location above be adopted. From the mouth of this pass, which is a mile in length, 

 and has a fall of 195 feet, the valley of Vallecitas has a regular descent at the rate of about 



