126 
GEOLOGY. 
seen at the summit, continues to extend on the left, and by its decomposition furnishes an 
excellent soil. We crossed many small streams, which furnish abundance of water to all parts 
of the valley, and permit the luxuriant growth of grass and oak trees. All the hills along the 
road were green with oaks 1 and chamizal, delighting the eye with their verdure after the 
pilgrimage on the Desert. 
Santa Isabel is a beautiful valley among the mountains, well watered, and bordered by groves 
of oak and other timber. It has a varied and undulating surface, and a good granitic soil. 
Adobe buildings of great size were erected here in the time of the Padres, but are now partly in 
ruins. They were, however, in part, occupied as dwelling and storehouses, the valley being 
used as a cattle rancho. The surrounding hills were hut sparsely wooded, hut were covered 
with dried grass, showing the presence of a deep soil and abundant verdure during the spring 
and early summer. 
December 18 .—Santa Isabel to San Pasqual, 23.5 miles. —Gray, compact granite, similar to 
that at Agua Caliente, was found in the vicinity of Santa Isabel. About seven miles beyond, it 
became more syenitic in its character, and the surfaces that had been exposed to weathering, and 
to decomposition in the soil, exhibited small, brilliant crystals of green hornblende, standing 
out in relief, having resisted decomposition better than the feldspar, in which they were im¬ 
bedded. Several miles beyond this point, on the side of the hill, the soil is colored red by a 
large amount of peroxide of iron, probably derived from the decomposition of pyrites. Frag¬ 
ments of quartz veins were also abundant. Large veins of feldspar and quartz were numerous 
along the road, and could he traced on the slopes of several ridges in the vicinity. Their white 
color showed distinctly through the green shrubs covering the hill-sides, and there appeared to 
he several nearly parallel veins. The first of these that was observed had a trend nearly north¬ 
west and southeast, magnetic. It appeared to he principally composed of coarsely crystalline 
feldspar, quartz, and tourmaline, with garnets, similar to the vein found on the other side of 
the divide at San Felipe. The feldspar in this vein, however, was more highly crystalline, and 
good crystals can he obtained there. The tourmaline, by its decomposition and abrasion, fur¬ 
nishes a large amount of black sand, which is distributed along the beds of the brooks and 
rivulets of the vicinity. 
Just before reaching the lagoon, the direction of the veins was found to he more nearly east 
and west, several of them having a trend of only five degrees north and west, magnetic. 
Observation of the trend of the granite at that point gave the same result. These quartz veins 
and the red soil so highly charged with iron were regarded as indicating the presence of gold, 
hut no examination or “ prospect ” could be made for it. We travelled very rapidly, and there 
was little opportunity for examination of the rocks beyond the trail. 
After winding about the hills by a very crooked road, we reached the Eancho of Santa Maria, 
a fine open valley or plain, with good grass and water. 
The observations made, under date of December 16, respecting the elevated valleys of the 
eastern slope of the mountains, will apply to this, the western side, also. The true character 
of the descent is not so distinctly visible as where the rocks and surface are almost entirely free 
from vegetation ; hut still it is evident, in descending towards tbe Pacific, that you pass succes¬ 
sively from a high plain to a low one by a sudden descent, showing the existence of stair-like 
elevations or terraces, very different from the character of the slopes of the Sierra Nevada. 
1 Leaves of a species of oak growing most abundantly along the valley were collected, and have been submitted to Dr. 
Torrey. He regards the oak as very near Q. inibricaria of the Atlantic States. 
