Little microscopic creatures, close kin to these nummulites, built the rocks in Egypt of which the Sphinx and Pyramids are made, and the enormous platform upon which they stand. These little animals also laid up the vast beds of building stone of which nearly all the great city of Paris is made. How did they do this? The little jelly-like creatures wanted covering for their frail bodies, and so gathered from the sea-water particles of lime and built them into shells. Millions upon millions of these shells fell down in layers on the sea-floor, and then water, weight, and heat became the forces to consolidate the myriads of shells into stone. The processes of earth-building are slow and long. The last world-building period, the Neozoic, had five ages. You will find their rather hard names on the plate which is our frontispiece. We might look at them as a splendid panorama. Shall we imagine that as fairies flitting through the woods; gnomes guarding the treasures of the earth; fair Pixies, floating in the rivers and seas; or giant Afrites standing in the hottest sunshine on the desert, we watch these five beautiful and wonderful ages roll on? What shall we see? Palms first: great tracts of palms, waving their feathery tops against the sky. The earth was warmer in those days than now, and plants and animals, now ranked as tropical, were found as far north as England. Not only were there palms widely spread, but cypress, plane trees, maples, elms, oaks, red-woods, figs, sweet gums, sour gums, tupelos, cinnamon and clove trees. The cape jasmine swung its censers of perfume; ferns and mosses made the woodland depths soft and green. Through these forests, and over the grassy plains, roved hyenas, wolves, bears, elk, antelopes. The famous mastodon was there, with many forms of deer, and thick-skinned creatures of the elephant and rhinoceros tribes that are now known no more. Along the river sides, among the sedges, were great wading birds, turtles, tortoises, crocodiles, serpents. Insects and birds increased, and here and there a monkey might be seen climbing among the tree-tops. As time moved on, a new, strange change overtook the earth. The climate in the Northern hemisphere became colder and colder; frost and snow held possession of lands that had hitherto been warm and sunny. Colder, still colder; what is called the Glacial or Frozen period was drawing on. As the atmosphere and soil chilled, fir, pine, birch, and dwarf willow succeeded to the palms; animals of woollier coats lived where the thick-skinned, smooth-coated, tropical animals had found a home. The ice-sheet, which at this day wraps the poles, began to extend southward, and an icy sea, such as now washes the shores of Greenland and the North Cape, rolled over the northern half of the globe.