Reports of explorations and surveys, to ascertain the most practicable and economical route for a railroad from the Mississippi River to the Pacific Ocean: Vol. 5, Pt. 2

GEOLOGY.
returned towards the mouth of Ocoya creek, and arrived in the evening, having had a hard
ride of about fifty miles. In numerous places over the plain there are dry water courses or
canals in the clay, and groves of dead cotton-wood trees. It is probable that the whole region
has been subject to overflow. It should be observed that the water of the slough, or lake, was
more or less saline, incrustations being found around the roots of the tufts of grass, where evapo ration had proceeded rapidly. Specimens of scoriaceous cinder, or volcanic slag, were also
found lying on the clay surface of the plain.
August 14, Sunday.-The thermometer indicated a temperature of 1020 in the shade during
the middle of the day; and a hot dry wind was constantly blowing from the west, following the
course of the valley of the creek.
Augu8st 15.-Examined the strata up the creek and on the right bank. The hills are in all
respects similar to those on the left. At one point, however, an outcrop of coarse-grained sand stone and conglomerate was found; it was harder than the other strata, and modifies the
outline of the hills. At sunset clouds were seen over the mountains at the east. The day was
unusually warm, the thermometer standing at 104~.
.August 16.-Collected more fossils, and made drawings of them; they are evidently Tertiary,
and probably quite recent-Miocene or Pliocene. Fresh water shells are abundant in the pools
of the creek, and specimens were preserved.
.Aulqgust 17 and 18.-Obtained the order of succession and lithological characters of the strata
forming one of the highest hills on the left bank of the creek. The edges are fully exposed in
several places, and in others are partly obscured by soil.' Just before sunset we had a short
shower, and the clouds looked very heavy over the mountains.
Augt8t 19.-Made more extended excavations in the bed of fossils, and procured five or six
additional species. Most of the specimens became broken and mutilated in taking them out
Some very large pectens were found, six inches in diameter; one of these was drawn by Mr.
Koppel. While he was turning over one of the masses of sandstone he was stung by a scorpion,
carrying a great number of little ones on her back. The application of a little ammonia water
quickly relieved the pain, and no further inconvenience was experienced.
-4ugust 20.-Found an additional number of species, and among them a shark's tooth.
Specimens of transparent selenite were obtained from the tops of some of the hills and from
the bed of the creek. The water in the deep holes has now become very low, and is strongly
impregnated with sulphur. It has the odor of sulphuretted hydrogen. Thermometer 103~ in
the shade. A comet was visible in the west this evening.
..4ugust 21.-The night was cold, and at sunrise the thermometer stood at 56 degrees. The
wind was blowing from the northeast, or down from the mountains, and this is generally the
case early in the morning.
Augaust 27.-I have been prevented by illness from making any geological observations for
several days. The sudden and great transitions from a temperature of 103~ and 104~ during
the day to 40~ and 500 at night, together with the use of stagnant~water, are sufficient to produce disease. On the evening of the 25th, I set up a pan of water in the shade of the brushshed, in order to determine, if possible, the rafe of the evaporation of water during the day.
The hunters came inl from the plains, bringing six fine carcases of deer and antelope, one of
them a fat buck, weighing, when skinned, 115 pounds, and his hind-quarters over 60. It was
of the black-tailed species.
1 This section is described in Chapter XIII.
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