CHAPTER X. 
FORT YUMA TO CARRIZO CREEK.-CARRIZO CREEK TO SAN DIEGO. 
Remarkable cleft in the rocks of pilot knob.—Terrace.—Sand hills.—Extent and height of the hills—Rain.—Rounded 
FORM OF THE GRAINS OF SAND.-AGATE AND QUARTZ.—SAND-STORM.-SlLICIFIED WOOD.-ARGILLACEOUS STRATA.-APPROACH TO 
CARRIZO CREEK.-BARREN MOUNTAINS WEST OF THE DESERT.-EROSION OF CARRIZO CREEK. —BANKS OF HORIZONTAL STRATA.- 
Fractures of the strata due to earthquakes.—Gypsum.—Stratum of marine shells.—Silicified wood polished by sand.— 
Palm springs.—Vegetation of the valley of the creek.—Granite and gneiss.—Vallecito.—Basin-shaped valleys at 
DIFFERENT ELEVATIONS -GNEISS AND MICA-SLATE -VEINS OF FELDSPAR TRAVERSING THE ROCKS.-LARGE CRYSTALS OF TOUR- 
• MALINE. SAN FELIPE. RAVINE NEAR THE INDIAN VILLAGE.—TRAVERTIN OF THE CREEK.—SANTA ISABEL. GRANITE. SYE¬ 
NITE.-- Quartz veins and indications of gold.—San pasqual.—Rounded hills of stratified formations.—Trap dyke.— 
Conglomerate —Slope from the mountains. -Valleys of erosion.—Beach shingle.—Fossil shells.—Punta loma.—San 
Pedf.o.—Bluff of argillaceous strata.—Bituminous shales.—Hard sandstone.—Sun cracks.—Modern deposits contain¬ 
ing shells.—Bitumen.—Santa Barbara.—Fossils. 
FORT YUMA TO CARRIZO CREEK. 
December 11 .—Fort Yuma to Cook’s Well. —We left Fort Yuma at noon for Cook’s Well, on our 
return across the desert, following, for the greater part of the way, the same trail over which 
we had passed in proceeding to the fort. 
At Pilot Knob, further observations were made upon the rocks and the adjoining hank of con¬ 
glomerate, and specimens collected. A great cleft, or fissure, about twenty feet wide, was 
observed in the mountain a few hundred yards hack from the road. It seemed to have been the 
result of volcanic disturbances,.hut was not followed or examined. We left the trail by which 
we came, which follows down the hank of the river, and turned into a trail on the right, leading 
among willow hushes and trees almost directly at the foot of the bluff or terrace of sand and 
conglomerate. The sand-hills commence near the knob, and extend all the way to the Indian 
village, and beyond it. On arriving at the village, it was found that the top of the hank wa i 
still formed of a conglomerate, and the loose dry sand of the Desert was pouring over it, reaching 
the cultivable land below. These sand hills were continually in view on the right hand, the 
trail in some places being at their base. On ascending them from the trail, and travelling 
among them, every other object was lost sight of, and nothing hut the wave-like outlines of the 
drifts could he seen. The steepest slope of all the hills was towards the south, and the northern 
slopes were found to he gradual—the sand gradually thinning down to the level of the plain. 
The highest hills, also, were on the south ; towards the north side of the belt the altitude of the 
hills decreased. The highest hills were probably about sixty feet, but some were seen in the 
distance which may have been higher. Tlie northern limit of the hills was seen, and the belt 
was probably less than half a mile in width. The progress of this sand towards the south 
appears to have been arrested by the steep hank and the mezquite trees. 
Before reaching Cook’s Well the sky became overcast with clouds, and rain began to fall. 
This is an uncommon occurence in that region and worthy of note. 
December 12.— Cook’s Well to Alamo Mocho. —It continued to rain through the night and during 
the morning, hut the fall was not great. We reached the Alamo about sundown. I carefully 
