First, we have the Devonian shores, with spreading fields of sea-weed and numbers of the club-shaped Algae of gigantic size. He has ventured, also, to represent a few trees, with scanty foliage; but I believe their existence at so early a period to be very problematical. Next comes the Carboniferous forest, with still pools of water lying between the Fern-trees, which, much as they affect damp, swampy grounds, seem scarcely able to find foothold on the dripping earth. Their trunks, as well as those of the Club-Moss trees which make the foreground of the picture, stand up free from any branches for many feet above the ground, giving one a glimpse between them into the dim recesses of this quiet, watery wood, where the silence was unbroken by the song of birds or the hum of insects. We shall find, it is true, when we give a glance at the animals of this time, that certain insects made their appearance with the first terrestrial vegetation; but they were few in number and of a peculiar kind, such as thrive now in low, wet lands. Upon this follow a number of sketches introducing us to the middle periods, where the land is higher and more extensive, covered chiefly with Pine forests, beneath which grows a thick carpet of underbrush, consisting mostly of Grasses, Rushes, and Ferns. Here and there one of the gigantic reptiles of the time may be seen sunning himself on the shore. One of these sketches shows us such a creature hungrily inspecting a pool where Crinoids, with their long stems, large, closely-coiled Chambered Shells, and Brachiopods, the Oysters and Clams of those days, offer him a tempting repast. Here and there a Pterodactyl, the curious winged reptile of the later middle periods, stretches its long neck from the water, and birds also begin to make their appearance. After these come the Tertiary periods: the Eocene first, where the landscape is already broken up by hills and mountains, clothed with a varied vegetation of comparatively modern character. Lily-pads are floating on the stream which makes the central part of the picture; large herds of the Palaeotherium, the ancient Pachyderm, reconstructed with such accuracy by Cuvier, are feeding along its banks; and a tall bird of the Heron or Pelican kind stands watching by the water's edge. In the Miocene the vegetation looks still more familiar, though the Elephants roaming about in regions of the Temperate Zone, and the huge Salamanders crawling out of the water, remind us that we are still far removed from present times. Lastly, we have the ice period, with the glaciers coming down to the borders of a river where large troops of Buffalo are drinking, while on the shore some Bears are feasting on the remains of a huge carcass.