TO YELLOWSTONE NATIONAL PARK. 125 
The laminated sandstone contains numerous irony concretions, from the size of a pea up to two 
inches in diameter. These are quite soft, and break readily, showing a concentric structure. The 
sandstone is much weather-worn. The limestone concretions, on exposure to the atmosphere, crack 
and break up so that the surface of the bluffs is strewn with their angular fragments. They do not 
particularly resemble the concretions of the Fort Pierre shales scen near Crooked Creek. 
Later in the day, to the northeast of the Moccasin Mountains, we passed over a good exposure 
of the Fort Pierre clays; and about three miles beyond this, but ata much higher level, were seen 
about 100 feet of white and yellow sandy clays, capped by a thin layer of fine grained calcareous 
brown sandstone. This latter was found in place only on the tops of the highest hills. A few 
shells characteristic of No. 4 were found in the Fort Pierre beds, but none of the other exposures 
examined yielded any fossils. All the beds seen during the day were substantially horizontal. 
The divide along which our road took us is for twenty-five miles a gently rolling prairie, covered 
with a fair growth of bunch-grass. It is a favorite feeding-ground for the buffalo; but, when we 
passed over it, only a few of these animals were seen, although signs of their recent presence were 
everywhere apparent. As we approach the Missouri River, the divide becomes less and less wide 
and the road more winding. Deep ravines and coulées from Dog Creek and the Judith River run 
back until they almost meet, so that the road becomes narrow and often difficult. About seven miles 
from the Missouri River there is a narrow pass, the only approach for wagons to the mouth of 
the Judith. Here the divide is only 10 feet wide, and on both sides steep and precipitous 
ravines run off to the east and west. This backbone continues for fifty or seventy-five yards, in 
which distance it turns and twists sharply every few fect. Sometimes the wagon on one side seems 
to hang over a precipice a hundred feet in height, while on the other it grinds along against the face 
of asandstone bluff elevated a few feet above the level of the road, or it has to be lowered carefully 
down an almost vertical slope of 30 or 40 fect, and to be dragged painfully up another as high and 
steep. From this point, a march of four miles over a gently rolling plateau brings us to the final 
descent into the Judith River bottom. The road down into the valley is long and steep; the 
difference in height between the top of the bluffs and the level of the valley being 1,200 feet. 
The upper 400 feet of the bluffs are composed almost wholly of beds of sand, white and yel- 
low, nearly pure, interstratified with occasional fragmentary layers of a fine-grained, clayey, brown 
or red sandstone. The beds of white sand contains a few poorly-preserved Unios and the remains 
of Dinosaurs (Hadrosaurus) and Turtles (Trionyx). The yellow sands contain many concretions of 
hard, yellow clay, but are without fossils, so far as examined. All the beds are horizontal, and 
most of them are quite hard. The white sands in some places change into a laminated white sand. 
stone, and seem to be always overlaid by the brown sandstone. At a lower level, these beds seem 
to pass into a white, firm, clayey sandstone, which is very hard ; but we were unable, in the limited 
time at our command, to fix the point at which the change took place. 
The character of the lowest portion of the beds on the Judith is much obscured by the pres- 
ence of the Fort Pierre clays in the valley, and by the washing out of the base of the bluffs and 
consequent dropping down of the rocks above them. This has taken place almost everywhere 
along the Judith and the Missouri Rivers at this point; and, in consequence of this, the rocks dip 
at every conceivable angle, and in all directions. A careful examination, however, will serve to 
convince the observer that all the beds are really horizontal, and that the apparent bendings and 
twistings of the rocks referred to by Dr.,Hayden are due simply to the action of running water. 
This element has here acted on a scale so enormous as to be almost inconceivable to one who is 
not familiar with the important part that is played by this agent in denudation in the West. 
At a time in the past;when the Judith carried much more water than it does at present, the 
undermining of the high bluffs was constantly going on, just as the higher alluvial banks of the 
Missouri River are being undermined at present; and, as the lowest beds were washed out, the 
superincumbent rocks slipped down in vast masses. The process, on a small scale, may be seen 
every day while ascending the Missouri. Besides this, the water, which in spring, from the melt- 
ing snows and the early rains, is carried by each of the thousand ravines which we find here, not 
only washes down the sides‘of the ridges, but works under the bluffs, often boring for itself an 
underground passage from one~coulée to another. Such passages increase in size annually, and 
finally become so large as not to be able to support the weight of the rocks above, which sink down 
