of sunken lines and raised edges, produced by the ephemeral streams, and a less complex series of horizontal ledges due to the prominent edges of hard layers. The steep slopes are worn into alcoves and irregular recesses by the transient rills, and smoothed or etched by the wind-driven sands. The result is an assemblage of architectural forms such as only the most fantastic dream pictures or the strange tricks of the mirage on northern ice-fields can simulate. Nor are the wonderfully intricate topographical forms the sole attraction. The rocks are variously coloured, and present endless combinations of yellow, red, green, purple, etc., in many tints and shades, rendered seemingly brilliant by contrast with the gray of shales and the blackness of occasional coal-seams. Owing to the burning of coal-beds, the rocks are sometimes altered over broad areas and given unusually striking colours, among which various shades of red predominate. Standing on some commanding crag in the Bad Lands in the early morning or when the purple shadows of evening fill the gorges and ravines, the most unimaginative traveller sees in the silence about him the ruins of a vast city, with cathedrals, temples, and palaces of varied colours and weird designs such as no mortal hand ever fashioned. It is at such times that the picturesque and gorgeous, although desolate, landscape kindles the fancy and suggests day dreams which distract one's attention from the more prosaic study of these earth ruins. The best developed portions of the strange region here referred to occur on the borders of the uplands overlooking the larger valleys, excavated by the rivers flowing eastward from the mountains, and are simply larger examples of erosion, such as may be seen in many bluffs and valley-sides in nearly every country, but rendered conspicuous by their size, extent, endless variety, and unusual colours.