And from all these periods, hidden in rocks and earth-beds, are frail remains of things that lived and perished long ago. Let us fancy that gnomes and genii keep these wonderful treasures. [Illustration: THE LOST BEASTS.] In the distribution of the plants and animals of past ages we read much of the earth’s history. For instance, when we find buried under the later soil of England, the bones of elephants and hyenas, and the leaves and fruits of palms or other tropical plants, we decide, on reasonable grounds, that at some period the climate of England has been warmer than it is to-day. Similarly, when in layers above these tropical specimens we find the relics of an Arctic vegetation, and the skeletons of elk and bears that belong only to polar or subpolar regions, we conclude that the days of tropical warmth in England were succeeded by days of polar cold. Again, when we find under the warm plains of South France the remains of animals and vegetables now belonging to Siberia, we say, “In former ages France had a reign of Siberian weather, for a period sufficiently long to permit the growth of Siberian plants and animals.” When we trace in regular succession the remains of such organisms back to the edge of the Polar circle, we say, “This northern cold, which once dominated all the hemisphere, slowly retreated to its present limits, and with it went its appropriate flora and fauna.” In all these instances the animals afford better indications than the plants, for plants have less capability than animals of adjusting themselves to new and untoward circumstances. If exposed to unusual cold or heat the plants die out, but many of the animals take thinner or thicker coats, to suit their new environment. Very nearly all the species of plants and animals belonging to the five cycles of earth-building preceding our own have perished. No doubt there were many of the early living organisms which disappeared and left no trace; the first ages may have been far more abundant in varieties than we imagine them to have been. Many hundred of different families have been found, and perhaps as many more flourished and utterly disappeared. We observe, concerning all these old-world families, that when once they perished they are, as we say, “gone for good”; a type does not disappear and reappear. As one description of animals became extinct, another was ready to take its place. This constant succession of animal types represents a constant approach to those creatures best fitted to occupy the earth with man. We have now on the earth large and destructive animals, as the rhinoceros, the hippopotamus, the lion, tiger, alligator, boa-constrictor, and others, but all of these “are tamed, or have been tamed, of mankind,” and constantly recede before the advancing demands of the human race for territory.