TO YELLOWSTONE NATIONAL PARK. 109 
which would otherwise exist. Further than this, while the trachytic hills are mostly bare and 
rocky, the other hills are, with the exception of the occasional sharp ridges of limestone, covered 
with grass and timber, so that little can be seen by one who must hurry on and make few stops. 
Probably two-thirds of the area of the hills is covered with trachyte, of which that found at Cone 
Butte may be taken as the type. 
CAMP LEWIS TO THE JUDITH GAP. 
From Camp Lewis, the road passes on thirty miles to the Judith Gap, crossing a portion of the 
country which has some promise of becoming valuable in time. Quite a number of running streams 
pass through it, of which Cottonwood Creek, Little Trout Creek, and Buffalo Creek are the most 
important. The latter becomes dry late in the season. Little Trout Creek is famous for the num- 
ber and beauty of the trout which it contains. In the immediate vicinity of the streams, the grass 
is excellent; but, on the higher prairie, it is rather thin. The streams flow fresh and cold from the 
neighboring Snow Mountains, and could doubtless be used extensively in irrigation. This Judith 
Basin is a region that has been highly spoken of, and it will no doubt in time furnish farms for 
hundreds of settlers. 
Very little opportunity for geological work is afforded over this portion of the route; for the 
prairie is much of it almost level, sloping away to the northwest to the Judith River, and giving 
no exposures of the underlying rocks. Considerable surface-drift is found here, which is entirely 
local, consisting, for the most part, of pebbles and masses of a blue limestone, some of them con- 
taining Carboniferous fossils. The source of this limestone is to be found in the Snow Mountains, 
whcib rise ten or twelve miles to the east, and from which it has been very abundantly carried off. 
A short distance before reaching Ross’s Fork, a bluff was examined, ofa black shale, containing 
many reddish iron concretions, but no fossils; and a little farther on, to the left of the road, were 
seen some washed exposures of light-gray shales, also without fossils. Not far beyond, the soil 
becomes red again; and, for a distance of several miles up to the Judith Gap, the presence of beds 
of red clay is indicated. Associated with them was a limestone, impure and knotty, with many 
veins of calcite. These red-clay beds appear also at the foot of the Snow Mountains, and, as has 
been said, also at the foot-slopes of the western end of the Judith Mountains. Their thickness seems 
to be small. They appear to belong to the Cretaceous, which doubtless extends under the grassy 
prairie from Camp Lewis to the Judith Gap. 
SNOW MOUNTAINS. 
From Buffalo Creek, ten miles before reaching the Judith Gap (that is, north of it), we made a 
short detour, to examine the west end of the Snow Mountains. This range extends in an approxi- 
mately east and west direction for a distance of some twenty miles. It is low, like all the other 
minor ranges. The average height can hardly be more than 2,000 feet above the surrounding 
prairie. Buffalo Creek takes its rise in the north side of the west end of the range. Following up 
the stream for a mile and a half from where the road crosses it, we found some outerops of sand- 
stone, with indistinct vegetable remains, undoubtedly Upper Cretaceous. A little farther—this on 
the north side—on the hill-tops, there was a gray sandstone, and below it, on the hill-side, a sand- 
stone of a deep yellow color. Both of these broke into irregular, wavy fragments. Dip 10° west- 
erly; strike north 20° east. These, which are in thickness perhaps 60 feet, are probably Upper 
Cretaceous. 
On the opposite (south) side of the stream appears a thinly-laminated sandstone, with a south- 
westerly dip of 10°, but a strike north 30° west. Beneath this followed the slopes of red soil, 
pointing to the presence of thin beds of clay beneath, like those at Camp Lewis. Following and 
underlying this was a firm, thick sandstone, breaking into massive slabs, which covered the top 
and sides of the hill, giving it much the appearance of having been paved; the strike was as before. 
Beyond, also south of the creek, a hard, gritty sandstone was noticed, with layers containing a large 
number of poorly-preserved shells. These were not specifically recognizable, but have been iden- 
tified as Cretaceous by Mr. Whitfield. Beneath this was what seemed to be a second deposit of the 
red-clay beds. These last are visible, though not so distinctly, on the opposite side of the creek, 
