16 
POOLE’S SURVEY FROM SAN DIEGO TO FORT YUMA. 
any given course, but is tortuous to tbe last degree, often nearly overlapping itself and forming 
numerous re-entering angles. Tbe heights of the summits are seldom over 5,000 feet. Between 
the foot-hills of the range are numerous fertile valleys, narrow and hounded by the slopes of the 
spurs on either side. Small rivers take their rise in the gorges of the hills, and flowing sea¬ 
ward, lose their waters in the sandy beds of their course, discharging no water into the sea 
except during the season of rains, when the supply of the element is greater than the demand 
of the thirsty earth. The different water-courses leading down from the mountains on the 
west have a general direction oblique to the coast, and nearly at right angles to the range. 
The principal streams in the vicinity are the Sweetwater and San Diego rivers, discharging 
into San Diego bay, the Soledad, San Diegito, and San Luis Rey, emptying into the ocean 
within forty miles north of San Diego, and the San Mateo, Santa Anna, and San Gabriel, 
further north, and in the neighborhood of Los Angeles, and south of the roadstead of San Pedro. 
It is evident that the most practicable passage for railroad communication through the moun¬ 
tains must be found by following up one of these streams from the coast to the lowest and 
nearest summit, thence across it to some valley or water-course leading to the desert. The two 
largest streams of those enumerated are the San Diego and San Luis Rey rivers. Both have 
their sources near the middle of the dividing ridge ; the former in a heavily timbered region, 
and the latter in the broad valleys of San Jose and Agua Caliente. Their courses are nearly 
parallel. The mouth of the San Luis is about 40 miles north of the port of San Diego, between 
which and the latter are a large number of natural obstacles to the construction of a road. 
The San Diego river falls into the bay of that name, coming from the mountains in nearly a 
straight course for a distance of about forty miles. This stream heads in the close vicinity of 
one of the most feasible passes yet known across the range, and its valley communicates with 
the summit by a gorge or canon. On the eastern or desert slope of the mountains is a parallel 
series of valleys or ravines, the most extensive of which are those of Vallecito and San Felipe, 
which are conterminous, though embracing distinct water-courses. There is a valley north of 
and parallel with San Felipe, as yet without a name, which receives the drainage of that valley 
and the Cayote valley ; further north is parallel with the other two. The latter is extremely 
difficult of access, and cannot easily be approached except from the desert. From the base of 
the mountains and the mouth of these valleys to the Colorado of the west lies the flat and sandy 
wilderness called the Colorado Desert. This is a belt of arid, level clay with a superficial 
covering of drifting sand, measuring 100 miles in width, extending north an indefinite distance, 
and terminated on the south by the shores of the Gulf of California. 
PRELIMINARY EXPLORATIONS. 
Under the direction of the officers of the railroad company, exploring parties were despatched 
to the interior to examine and report upon the different routes and passes supposed to be favor¬ 
able to the proposed construction. Commencing at the southernmost of the routes suggested, 
that of Sweetwater valley, connecting with the pass of Jacumba, it was as carefully and dili¬ 
gently examined as the time and means of the company would allow. Uo pass of probable 
feasibility was found ; that from Jacumba to the Desert being rough and precipitous, and there 
being encountered no other entering valleys on that side of the mountains of sufficient direct¬ 
ness to admit of a choice in that direction. The peculiarly broken nature of the ground, 
