Some of you, I dare say, are fond of some branch or other of natural history, and perhaps you may be in the habit of collecting shells, plants, insects, or fossils. Well, I hope a great many of you do so, for it is a very delightful employment, when you are not learning your regular lessons. When I was a school-boy, I loved to dig fossils out of the earth, and many a sunny day have I spent with my hammer and chisel under the cliffs by the sea-side, or in a stone-quarry. Many times I laboured long without success, but at last I scraped together a very pretty collection, and always managed to enjoy myself on these fossil-hunting days, whether I was successful or not. But what I want particularly to say to you before we part is, that I hope none of you will rest satisfied with merely listening to what others tell you, with making an orderly collection of specimens, or recollecting merely the outsides of things. Though all these are very good when in their proper places, they are not enough. You should compare together different facts, and often turn them over in your minds, always keeping in view that there is something to be learned from them more interesting and more important than any knowledge, however correct, respecting the shapes of crystals, shells, or plants, or the habits of animals. If you are diligent in thinking on what you know, you will see that nothing stands alone in nature; every single thing is connected with other things, so as to make up one great whole. It is true that you will sometimes see what seems to be an exception to this; you will see instances of conflict and disorder, and, as it seems, things destroyed without a reason; but you will also very often find, as you come to know more, that what seemed at first an exception was not such in reality, and that it was what tends as much to the order and beauty of the whole, as any of the particular things you admired at first. II. The ancients supposed that those parts of the world which were in the torrid zone, and those towards the North Pole, could not be inhabited by man; and we find from their writings, that it was something of a puzzle to know of what use they could be. They did not, however, know much about the extent of them, for even the shape of the earth was then unknown,--some contending that it was in the form of a cylinder, some that it was pear-shaped, and others that it was round and flat like a trencher. A very few made a shrewd guess at its true figure. No one was quite certain on the subject, till navigators had sailed round it, so as to reach, by continually going forward, the same spot as they started from.