Behold the tumble-bug with her ball of dung by the roadside; where is she going with it? She is going anywhere and everywhere; she changes her direction, like the vine, whenever she encounters an obstacle. She only knows that somewhere there is a depression or a hole in which her ball with its egg can rest secure, and she keeps on tumbling about till she finds it, or maybe digs one, or comes to grief by the foot of some careless passer-by. This, again, is Nature's way, randomly and tirelessly seeking her ends. When we look over a large section of history, we see that it is man's way, too, or Nature's way in man. His progress has been a blind groping, the result of endless experimentation, and all his failures and mistakes could not be written in a book. How he has tumbled about with his ball, seeking the right place for it, and how many times has he come to grief! All his successes have been lucky hits: steam, electricity, representative government, printing--how long he groped for them before he found them! There is always and everywhere the Darwinian tendency to variation, to seek new forms, to improve upon the past; and man is under this law, the same as is the rest of nature. One generation of men, like one generation of leaves, becomes the fertilizer of the next; failures only enrich the soil or make smoother the way. There are so many conflicting forces and interests, and the conditions of success are so complex! If the seed fall here, it will not germinate; if there, it will be drowned or washed away; if yonder, it will find too sharp competition. There are only a few places where it will find all the conditions favorable. Hence the prodigality of Nature in seeds, scattering a thousand for one plant or tree. She is like a hunter shooting at random into every tree or bush, hoping to bring down his game, which he does if his ammunition holds out long enough; or like the British soldier in the Boer War, firing vaguely at an enemy that he does not see. But Nature's ammunition always holds out, and she hits her mark in the end. Her ammunition on our planet is the heat of the sun. When this fails, she will no longer hit the mark or try to hit it. Let there be a plum tree anywhere with the disease called the "black-knot" upon it, and presently every plum tree in its neighborhood will have black knots. Do you think the germs from the first knot knew where to find the other plum trees? No; the wind carried them in every direction, where the plum trees were not as well as where they were. It was a blind search and a chance hit. So with all seeds and germs. Nature covers all the space, and is bound to hit the mark sooner or later. The sun spills his light indiscriminately into space; a small fraction of his rays hit the earth, and we are warmed. Yet to all intents and purposes it is as if he shone for us alone. II BIRD-SONGS