TO YELLOWSTONE NATIONAL PARK. 127 
layers of yellowish laminated sandstone, is seen, the whole about 50 feet in thickness. No fossils 
were found in either of the above. 
It may be stated in general terms that the lower two-thirds (or 800 feet) of these bluffs consist 
of yellowish clays, interstratified with thin layers of sandstone and limestone, and that the upper 
400 feet is almost wholly sandstone, more or less hard, generally white, but sometimes varying from 
that to a dark brown. Lignite occurs in the upper sandstone. A few hundred yards from our 
camp we noticed a bed of sand 15 feet thick, with several layers of impure lignite from 1 to 2 inches 
in thickness running through it. This bed had slipped down from some point high up on the blufts, 
as it had no connection with the neighboring rocks, and had quite a steep dip. From the fossils 
obtained, it seems that the upper beds of sands and sandstones must be referred to what have been 
called the Fort Union Beds, or No. 6 of the Cretaceous. 
It is a matter of regret to the writers that the observations at this point were so few and so 
disconnected as to give but little idea of the structure of the bluffs and the relations of the beds. 
The extent of country to be covered by our observations was very large; and patient study and 
observation, extended over a considerable time, would have been required to do justice to the 
locality. 
LITTLE ROCKY MOUNTAINS. 
A delay of a few days at Carroll on our return journey was in part utilized by a short excursion 
to the Little Rocky Mountains, which lie about twenty-five miles from the Missouri River, almost 
due north of that settlement. The starting-point was a short distance below Carroll; and, ou reach- 
ing the north bank of the stream, we took a trail leading to Milk River, which we were able to 
follow for some distance. The road rises quite steeply on first leaving the alluvial plain of the river, 
aud attains 400 feet of its final height within a very short distance. From here the rise is more 
gradual, the road winding to and fro, keeping on the summit of a narrow ridge, whose sides are 
washed down steeply on either hand. The wasbing-out of the bluffs was here even more striking 
than where observed on the south side of the Missouri; and the continually dividing and subdi- 
viding coulées form a labyrinth of little ridges and valleys, which would present a peculiar appear- 
ance could they be viewed from a point a few hundred feet directly above. The course for the road, 
however, has been so well chosen that the ascent is continuous; no descent into any minor ravines 
being necessary. The final rise is a matter of time, and the high plateau which forms the true bank 
of the river is only reached after a ride of several miles. The height at this point, as given by an 
aneroid, was 680 feet above Carroll, which corresponds closely with the similar measurements taken on 
the other side. After a little comparatively level prairie, the gradual rise is continued, and at the 
foot of the hills the height is 1,250 feet above the river. A section from Carroll to the mountains 
is given in figure 13, which it is interesting to compare with figure 4; the scale is the same. 
Fig. 13. 
Trachytic Hill 
Little Rocky Sits. 
Missouri R. 
Profile section from Carroll to the Little Rocky Mountains. Course North and South. 
Distance direct about 25 miles. , 
The bluffs on the north bank are made up entirely of Fort Pierre shales, and these were observed 
from time to time nearly up to the mountains. In general character, they do not differ from those 
before described. The surface of the prairie as we pass from the river is covered far and wide with 
drift, very similar to that observed on the south side of the stream; though here the quartzite pebbles 
are even more numerous, and cover the surface of the ground so thickly as almost to have crowded 
