It is the wholesomest, most inspiring reading in all the world, this Book of Nature. And there is simply no end to it. Just see what all we've been led into merely in following out the story of a grain of dust; and even then, I've only dipped into it here and there, as you can see by the hints of things to be looked up in the library. If we had gone into all the highways and byways of the subject--for it's all one continued story, from the making of the planets, circling in the fields of space, to the making of the little dust grains that are whirled along in the winds of March--if we followed the story all through we would have to have learned professors to teach us Astronomy, Geology, Chemistry, Zoology, with its subdivisions of Paleontology, Ornithology, Entomology, and so on; a whole college faculty sitting on a grain of dust! III. THE WORLD BROTHERHOOD An obvious thing in Nature is what is called "the struggle for existence"; animals and plants fighting among themselves and against enemies of their species in the universal struggle for food. What is not so obvious, is how the whole world of things works together toward the common good. HOW THE LICHENS AND THE VOLCANOES WORK TOGETHER For example, working with those quiet little people, the lichens, is one of the biggest and noisiest things in the world--the volcano. The volcanoes not only pour into the air vast quantities of carbon-gas, which is the breath of life to plants, but help the lichens and the rest of the soil-makers with their work in other ways. And as the volcanoes help the lichens get their breath, the lichens forward the world service of the volcanoes by turning their lava into soil; in course of time, hiding the most desolate of these black iron wastes under a rich garment of green. It is thus the dead lava comes to life, and it is the very smallest of the lichen family that starts the process. [Illustration: _Courtesy of the Northern Pacific Railway_ HOW THE DEAD LAVA COMES TO LIFE Lava, after it has been converted into soil, by the agents of decay, makes the richest land in the world. This picture shows a vineyard on the fertile plains overlooked by Mt. Ranier, which is an extinct volcano. In the days when Mt. Rainer was being built these plains were covered with molten lava.] Among the two principal gases of the air there is a working brotherhood; just as there is between the plants and the animals in their great breath exchange. The oxygen in the air makes a specialty of crumbling up rock containing iron. It rusts this iron into dust; while the CO_{2}, as the High School Boy calls what I have called carbon, for short, goes after the rocks that contain lime, potash, and soda. Working with both these gases is the frost that, with its prying fingers, enlarges the cracks in stones, and so allows the gases of the water and the air to reach in farther than they could otherwise do.