sides, the strata have evidently never been disturbed in such a way as to afford any great variety of altitude in this locality. We are therefore shut up to the conclusion that, at the time these leaves were green, a climate prevailed very different from any now known in the same 
Fig. 12.—Cornus rhamnifolia (O. Weber). The climate must have been warm and equable. Indeed, that the climate, not of Dakota only, but of the whole northern hemisphere, was at one time far milder than now seems proved, for leaves such as these of which we speak have been found in Greenland and many other circumpolar lands. What may have been the prime cause of this former high temperature in high latitudes we leave students of physical geography and surface geology to decide, but we may say this: the warm and equable climates of the world are maritime, or characteristic of islands, as the climate of Italy or the Grecian Archipelago. That a large body of fresh water may work wonders in temperature and amount of moisture, is to us a familiar fact witnessed by the climate of the peninsula of Michigan. And so, to meet the requisite climatic conditions suggested by these few leaves, we are ready to accept without doubt the statements of men who from their study of the topography of the Bad Lands declare the whole region to have been, perhaps again and again, the bed of a wide-spread inland lake or sea. On the shores and islands of this Mediterranean of the Western world stood the forests primeval whose foliage has come down to us like the sad memory of better days.
As one looks upon these fairly outlined relics of a long-forgotten age, he may catch glimpses of landscapes in presence of which all the bleakness and barrenness of the present disappear. Instead of sterile hills and buttes, far stretches the quiet sea, unvexed by storms, but filled with happy islands like the "Islands of the Blest." Over the islands the laurel blooms, abundant fig-trees spread their dense and shining foliage, and send down aerial roots in thickets impenetrable. Along the curving shores the bending willows sweep the water's surface, while hard by stands the broad-leaved plane-tree and the feathery elm, and farther back the hazel and its kindred oak. The poplar shakes its shining leaves and fills the air with fragrance. Over the cornel and the hornbeam creeps the vine, and high above all, walling the horizon like the cryptomeria in the forests of Japan, sequoias, magnificent se-
