SOME AMERICAN MONSTERS. 157 
earth or rising ground. It is also applied in a limited sense to 
the more prominent irregularities of the deeply sculptured slopes 
of the larger terraces. ‘These buttes, therefore, vary in extent, from 
a mere mound rising slightly above the level of the plains to hills 
of varied configuration reaching to the level of the broader buttes 
or terraces. 
The débris resulting from the continual wearing away, or 
demolition of these buttes and terraces, now lies spread out on 
the plains below. From the lower plains the smaller terraces 
appear like vast earth-work fortifications, and when not too much 
cut up by erosion, remind one of long railway embankments. 
But in many cases the terraces are so much cut up by narrow 
ravines that they appear as great groups of naked buttes rising 
from the midst of the plain. Nothing can be more desolate in 
appearance than some of these vast assemblages of crumbling 
buttes, destitute of vegetation, and traversed by ravines, in 
which the watercourses in midsummer are almost all dried up. 
To these assemblages of naked buttes, often worn into castellated 
and fantastic forms, and extending through miles and miles of 
territory, the early Canadian voyageurs gave the name Mauvais 
Terres. ‘They occur in many localities of the Tertiary formations 
west of the Mississippi River. Professor Leidy, who with two 
friends made an expedition in search of fossils to Dry Creek Cafion 
in this region of the “ Bad Lands,” about forty miles to the south- 
east of Fort Bridger (Wyoming), thus describes his impressions :— 
“On descending the butte to the east of our camp, I found 
before me another valley, a treeless barren plain, probably ten 
miles in width. From the far side of this valley butte after butte 
arose and grouped themselves along the horizon, and looked 
together in the distance like the huge fortified city of a giant 
race, the utter desolation of the scene, the dried-up watercourses, 
the absence of any moving object, the profound silence which 
prevailed, produced a feeling that was positively oppressive. 
When I thought of the buttes beneath our feet, with their 
