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SPRINGS IN THE DESERT—CALCAREOUS INCRUSTATION. 99 
4 a. m. the temperature of the spring was 56° and the air 52°. Our course was directed towards 
a projecting spur of the mountains, supposed to be about ten miles distant. The ground was 
principally clay, which by drying in the sun has become very hard, but on being cut and 
pulverized by the passing of the train became dusty, like dry ashes. On cutting down into it 
for about twelve inches it was found to be more sandy and micaceous, and a specimen was taken 
for analysis, (No. 263 of the catalogue.) It appeared to be a rich soil, for wherever water comes 
to the surface the vegetation is abundant, and a large area near the mountains was covered with 
a dense growth of weeds, the ground being moist. 
Eight or nine miles from our camp at the villages we stopped at another spring, where the 
water rose to the surface in abundance, and formed a pool twenty feet or more in diameter, 
surrounded by an artificial embankment three or four feet high. The water was clear and 
good; its temperature at noon was 78°, and there appeared to be a never-failing supply. 
Indians were living here also, and appeared to have a good store of grain and melons, which 
they had raised in the vicinity. We remained at the spring until three o'clock, to rest the 
animals and prepare for a long march over the unknown region between us and Carrizo creek, 
where the emigrant road from the Gila enters the mountains. None of the Indians could be 
induced to go with us; they were afraid to venture, saying that there was neither grass nor 
water, and that we could not take the wagons. The mountains on the right extended off in 
spurs or long ridges, one beyond the other, exactly as before observed from the camp at Deep 
Well. Carrizo creek was supposed to lie beyond one of the distant spurs, and we travelled 
towards it, having taken the precaution to fill all our canteens with water. 
About sunset we passed within two miles of a projecting spur of the mountains, upon which 
the water-line was remarkably distinct. Although it was evidently high above the general 
surface of the plain or slope, it looked as if it could be easily reached, and I left the train to go 
and take its altitude with the barometer. On arriving under the rocks 1 was astonished to find 
that those which had appeared so small and diminutive, in the distance, were huge masses of 
granite, from ten to thirty feet in diameter, piled confusedly together, leaving many large 
spaces and long galleries among and between them. The whole surface was covered with 
the white incrustation, so that the rock was completely hid from view. At many of the over- 
hanging projections of the rocks this incrustation had become detached, by its great weight, 
and had fallen down to the foot of the cliff in large blocks. These disclosed the fact that this 
calcareous investment was, in some places, nearly two feet in thickness. 
The interior portions of this crust, that adjoined the surface of the rock, were more compact 
and solid than the outer parts; and, here and there, through the mass, a small spiral shell was 
enveloped. The outer parts of the masses were more open, and traversed by an assemblage of 
irregular tubes and channels; these extended to the surface in horizontal lines, and produced 
a series of irregular and convoluted openings, which give a peculiar coralline aspect to the 
mass and cause it to resemble an organic growth. 1 observed, also, that this crust was more 
highly developed, and that its thickness was much greater en the under or overhanging 
surfaces than an the upper portions of the rocks. It is difficult to give a satisfactory explana- 
tion of the cause of this peculiarity, and of the singular form of the outer surface of the crust, 
without supposing it to be organic in its origin. Its internal structure is not consistent with 
this hypothesis, as it appears to have been deposited in successive coats, one over the other, as 
if from waters highly charged with carbonate of lime. The peculiar tubular structure may 
have been, and probably was, produced by the roots or stems of aquatic planta. But, even if 
this were so, it is difficult to conceive how such extreme regularity should be given to all the 
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