ATMOSPHERE.—SOIL. 
7 
humidity in the atmosphere not before existing. In the States there is scarcely a night when 
the moisture will not collect on the glass exposed to the air, sufficient in two or three minutes 
to prevent the perfect transmission of light. 
November 9.—The effect of last night’s dampness was felt in the morning, for, although the 
thermometer was only 37°, the cold was more sensible than in the dry regions at 25°. 
We started in advance of the command to explore the lower belt of mountains by which we 
were encompassed. The first thing we noticed in the gorge was a promontory of pitch-stone, 
against which the river impinged with fearful force, for it was now descending at a rapid rate. 
Mounting to the top of the rock, on a beautiful table, we found sunk six or eight perfectly sym¬ 
metrical and well-turned holes, about ten inches deep and six or eight wide at top; near one, 
in a remote place, was a pitch-stone, well turned and fashioned like a pestle. These could 
be nothing else than the corn-mills of long extinct races. Above this bed of pitch-stone a butte 
of calcareous sandstone shot up to a great height, in the seams of which were imbedded beauti¬ 
ful crystals of quartz. Turning the sharp angle of the promontory, we discovered a high per¬ 
pendicular cliff of calcareous spar and baked argillaceous rock, against which the river also 
abutted, seamed so as to represent distinctly the flames of a volcano. A sketch was made of it, 
and is presented with these notes. On the side of the river opposite the igneous rocks, the 
butte rose in perpendicular and confused masses. 
This chain continued, not parallel, as I supposed, to the first described barrier, but circled 
round to the east, and united with it. It also united on the north side, forming a basin three or 
four miles in diameter, in which we encamped last night. Except a few tufts of larrea Mexi- 
cana, these hills were bare of vegetation. Away off to the south, and bordering on the banks 
of the river, covering the surface of the ground for one or two feet, was an incrustation of black 
cellular lava or basalt, like that seen about the Raton. Nothing more was wanted to give the 
idea of an immense extinct volcano. Through the centre of the crater the Gila now pursues its 
rapid course. 
The Gila at this point, released from its mountain barrier, flows off quietly at the rate of 
three miles an hour into a wide plain, which extends south almost as far as the eye can reach. 
Upon this plain mezquite, chamiza, the green acacia, prosopis, artemisia, obione canescens, and 
pitahaya, were the only vegetation. In one spot only we found a few bunches of grass. More 
than four-fifths of the plain was destitute of vegetation ; the soil, a light-brown, loose, sandy 
earth, I supposed contained something deleterious to vegetation.* 
We made our noon halt at the grass patch. At this place were the remains of an immense 
Indian settlement; pottery was everywhere to be found, but the remains of the foundations of 
the houses were imbedded in dust. The outlines of the acequias, by which the soil was irrigated, 
were sometimes quite distinct. 
The soil was moist, and wherever the foot pressed the ground the salts of the earth effloresced, 
and gave it the appearance of being covered with frost. In this way the numberless tracks of 
horses and other animals, which had at times traversed the plains, were indelible, and could be 
traced for great distances by the eye, in long white seams. 
We found fresh trails of horses, which might be those of General Castro, or of the Indians. 
When leaving California, Castro’s determination, as we learn from Carson, was to go to Sonora, 
beat up recruits and return. Our route might easily be reached, for we are now marching along 
a road everywhere accessible, and within three days’ march of the settlements of Sonora and 
the fort at Tucson, said to be regularly garrisoned by Mexican soldiers. 
We passed the deserted lodges of Indians, and, at one place, remote from the lodges, we saw 
thirteen poles set up in a sort of incantation formula—twelve on the circumference of a circle 
* A specimen of this soil was submitted to Professor Fraser, who says: “ It is a light-brown, loose, sandy earth, containing 
scarcely anything soluble in water, the solution giving only faint indications of common salt and carbonite of lime. A very 
small portion of iron pyrites is also contained in it, but I imagine its want of fertility may more properly be attributed to its de¬ 
ficiency in organic matters.” 
