“There rolls the deep where grew the tree, O earth, what changes thou hast seen! There where the long street roars, hath been The eternal stillness of the sea. “The hills are shadows, and they flow From form to form, and nothing stands; They melt like mist, these solid lands, Like clouds they shape themselves and go.” --TENNYSON, _In Memoriam_. We have been studying for some time about earth-building. We have learned a little of how the rocks and the soil of our globe were formed. What is that study of earth-building called? It is called Ge-ology, which means earth-lore or history, for the old Greeks called the earth Ge, and ge-ology just means the story of earth-making. But in these lessons we have been talking not of the rocks and earth-beds, but of the gnome-treasures hidden therein, the bones, patterns, stone images, burial cases of things that lived long ago. This is a new study, and is a very important branch of geology; for unless we learn about these old organisms and understand what they tell us, we cannot well learn our geology. These fossils shut up in the rocks are the writings or pictures which keep the story of the long ago. This study has been given the long name of Palæontology--it merely means the study or lore of fossils. But pray what are fossils? We have heard much about them. What are they? The word fossil really means a thing “dug up.” Once it was applied to any kind of mineral substance. Now we mean by fossil organized substances or their imprints, which have been preserved in any natural fashion, that is, not by the art of man, but by nature. The study of fossils embraces the study of all forms, from the most ancient here in the rocks of the Dawn, or first period, to those which may have only been buried for a few score of years. Thus you may see in a cabinet a bit of limestone full of ancient foraminiferæ, and near it a fossil clam from some bed in southern New Jersey, which was producing living clams one or two hundred years ago. The study of fossils does not assert any limit as to the grade of an organism. A fossil may be some large and curious fish, a rare bird, a beautiful stone lily, or merely a lump of resin which long ago dropped from some tree of the coal period. So also, we have fossil leaves, fruits, roots, fossil rain-marks, fossil footprints, fossil worm-casts and burrows, and little fossil cases of caddis-worms. Some very valuable fossils are called coprolites; these are the droppings of digested or partly-digested food of animals, and they are valuable because they often contain traces or portions of plants or animals, upon which these other creatures fed, and which now would be entirely unknown unless preserved in this way.