GENERAL DEDUCTIONS. 
4 L 
I arrived at the Mission of San Diego on the 19th of December. This mission is located in a 
long, narrow valley, formed by the streams descending the slope, and is now occupied as a 
military post. There is a fine grove of olive-trees in front of the mission buildings.—(See 
Plate XII.) 
On the 20th of December Lieutenant Parke came in. He reported that he had followed to 
the sea the creek which rises in Warner’s Pass, and found it emptied near the Mission of San 
Luis Bey. The creek in many places passed through rocky canons impassable for mules, and 
Lieutenant Parke is of the opinion that it is unfit for railroad purposes. Leaving San Luis 
Eey, he travelled near the coast to San Diego, and here he could gain no information of any 
other pass than the Jacum Pass. He therefore made a rapid reconnaissance of this pass, and 
became convinced it was utterly impracticable. The mountains were high and rugged, and it 
was almost impossible to travel on muleback off the trail. 
From all that I saw and could learn, I am forced to the belief that there is no pass leading 
directly into San Diego. To demonstrate this without a doubt, a detailed examination must be 
made, and if properly done should occupy three or four months of field duty. But a very small 
party would be required for this work, and the result would be a good topographical map of the 
country. 
The field-work of the expedition being now concluded, the party was discharged, with the 
exception of the scientific corps, who, with myself, proceeded to San Francisco to compile the 
notes of the survey, and prepare a report. 
GENEBAL DEDUCTIONS. 
In the foregoing description of the portions of country surveyed, I have endeavored to show 
the nature of the passes, &c., by numerical data, so that any one may be able to judge as well 
as myself of their adaptability for railroad purposes. I will now endeavor to state what, in 
my opinion, are some of the neeessary results of the conformation of the country as it has been 
shown to exist. 
Under the supposition that a road has been constructed from the Mississippi river to the mouth 
of the Gila, if the question is simply how to continue that road to the Pacific, the answer is at 
once apparent. It would follow a nearly direct line to the entrance of the San Gorgonio Pass, 
the best in the Coast range ; then through that pass to the San Bernardino valley ; and from 
there to San Pedro, or some other point in its vicinity on the coast. But the port of San Pedro 
has no harbor ; and, in fact, the only really good harbors on the coast of California are those of 
San Francisco and San Diego. It hence becomes advisable to examine into the best routes to 
these two places. 
To go from the mouth of the Gila to San Francisco, we must still go through the pass of San 
Gorgonio, unless we follow up the Colorado river, till we can find a place to leave it, and cross 
the Basin to the mountains. This latter route is mostly unexplored ; but it is believed the 
difficulties of crossing the Basin will cause the preference to be given to the former. Having 
arrived in the San Bernardino valley, the road must either follow near the coast, or it must 
recross the Coast range, cross the Sierra Nevada, and enter the Tulare valley. Whether there 
be a practicable route in the Coast range or not, is a problem as yet unsolved. A party is now 
in the field surveying that portion of the country. To follow the other route we must cross 
from the valley of Los Angeles to that of Santa Clara, and thence by the New Pass to the 
