26 COMPARISON OF PASSES. 
with the Coast range. The ridges of the latter curve around the southern end of the Tulare 
valley and form its boundary. At the foot of these ridges, and on the south side of the 
entrance to the pass, there are low rounded hills, much cut up by ravines, and often present- 
ing precipitous banks, apparently of clay. (See Plate VII.) Mr. Blake describes these hills as 
of sedimentary origin, and of the age of the Tertiary. After entering the pass, we ascend a 
stream flowing from it into the Tejon, fed by springs situated about half way to the summit. 
In the ravine of this brook the bases of the mountains approach closely, forming but a narrow 
valley ; but still ascending beyond the springs, the valley opens out to a plain from one-half to 
three-quarters of a mile in width, and the ascent is less steep. When quite near the summit, 
the ascent becomes more abrupt for a short distance. Descending from this divide, we come 
upon waters flowing into the Santa Clara river, and thence into the Pacific. Some distance 
beyond we come to another small divide, ی‎ HE from the summit of which we are upon the 
waters flowing into the Basin. 
From a short distance beyond the summit to the Great Basin, the valley of the pass is wide 
and bounded by low hills. Near our last camp in the pass the broad expanse of the Basin was 
visible, broken here and there by isolated ridges of barren rocks. 
From the western entrance of the pass to the springs at the source of the brook, a distance of 
five and a quarter miles, the grades are quite steep, averaging 302 feet to the mile, the maxi- 
mum being 348 feet, and the minimum 229 feet. From the springs to near the summit, the 
average grades are 121 feet to the mile, while at the summit itself there is for half a mile an 
ascent of 339 feet per mile, and for three-quarters of a mile a descent at the rate of 441 feet per 
mile. No difficulty is then experienced till we arrive at the second divide, which separates the 
waters flowing towards the Pacific from those flowing towards the Basin. Here we had a 
descent for half a mile at the rate of 357 feet per mile, after which the descent is gradual to the 
Basin. 
The main difficulty in this pass is the very steep grade in the bed of the brook. The hills on 
either side are cut up by deep ravines—so much so as to prevent recourse to side-cuttings. The 
two divides are easily passed by tunnels from a halt' to one and a quarter mile in length. 
There is a good wagon-road through this pass; and I learn that, since our survey a military 
post has been established at or near the springs. 
GENERAL REMARKS ON THE PASSES OF THE SIERRA NEVADA. 
In the foregoing general description of the most important of the passes examined in the 
‘Sierra, I have spoken of only the most important features of each pass, giving their grades, 
and endeavoring to explain the position and peculiarities of each, so that a general comparison 
may be made. This was all that was necessary, as the accompanying tables give in a concise 
form full and minute information, as also the data from which this information was obtained ; 
and these tables, in connexion with the maps and profiles and the sketches, form a complete 
description of the passes. I think the facts which have been brought forward warrant the 
following conclusion : 
Of the five principal passes described, there are two which are pre-eminently superior to the 
others, viz: the Tah-ee-chay-pah Pass and the Cañada de las Uvas. As far as the situation of 
these passes is concerned, neither has the advantage if the road comes from the Mohave or the 
mouth of the Gila; for, taking a point on the map near which such a road must pass, and 
Vide Report upon the Geology of the Expedition. 
