"On the high plateau that lies to the west of the Rocky Mountains, along the southern borders of the Wyoming territory, the traveller moving westwards begins to enter on peculiar scenery. Bare, treeless wastes of naked stone, rising here and there into terraced ledges and strange tower-like prominences, or sinking into hollows where the water gathers in salt or bitter pools. Under the cloudless sky, and in the clear dry atmosphere, the extraordinary colouring of these landscapes forms, perhaps, their weirdest feature. Bars of deep red alternate with strips of orange, now deepening into sombre browns, now blazing out again into vermilion, with belts of lilac, buff, pale green, and white. And everywhere the colours run in almost horizontal bands, running across hollows and river-gorges for mile after mile through this rocky desert. The parallel strips of colour mark the strata that cover all this wide plateau country. They are the tints characteristic of an enormous accumulation of sedimentary rocks, that mark the site of a vast Eocene lake, or succession of lakes, on what is now nearly the crest of the continent." In this strange region the flat-topped hills, table-lands, or terraces, as they are variously named, seen from lower levels, are usually called "buttes," especially when they are of limited extent. This name is of French origin, and signifies a bank of 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 Cañon in this region of the "Bad Lands," about forty miles to the southeast of Fort Bridger (Wyoming), thus describes his impressions:--