Motion or change, and identity or rest, are the first and second secrets of nature: Motion and Rest. The whole code of her laws may be written on the thumbnail, or the signet of a ring. The whirling bubble on the surface of a brook, admits us to the secret of the mechanics of the sky. Every shell on the beach is a key to it. A little water made to rotate in a cup explains the formation of the simpler shells; the addition of matter from year to year, arrives at last at the most complex form; and yet so poor is nature with all her craft, that, from the beginning to the end of the universe, she has but one stuff— one stuff with its two ends, to serve up all her dream-like variety. Compound it how she will, star, sand, fire, water, tree, man, it is still one stuff, and betrays the same properties.   - Ralph Waldo Emerson