The Germans imagine that they have fairy kobolds, sprites, and gnomes which play under ground and haunt mines. I know a real one. I will give you his name. It is called "Gravitation." The name does not sound any more fairylike than a sledge hammer, but its nature and work are as fairylike as a spider's web. I will give samples of his helpful work for man. In the mountains about Saltzburg, south of Munich, are great thick beds of solid salt. How can they get it down to the cities where it is needed? Instead of digging it out, and packing it on the backs of mules for forty miles, they turn in a stream of water and make a little lake which absorbs very much salt--all it can carry. Then they lay a pipe, like a fairy railroad, and gravitation carries the salt water gently and swiftly forty miles, to where the railroads can take it everywhere. It goes so easily! There is no railroad to build, no car to haul back, only to stand still and see gravitation do the work. How do they get the salt and water apart? O, just as easily. They ask the wind to help them. They cut brush about four feet long, and pile it up twenty feet high and as long as they please. Then a pipe with holes in it is laid along the top, the water trickles down all over the loose brush, and the thirsty wind blows through and drinks out most of the water. They might let on the water so slowly that all of it would be drunk out by the wind, leaving the solid salt on the bushes. But they do not want it there. So they turn on so much water that the thirsty wind can drink only the most of it, and the rest drops down into great pans, needing only a little evaporation by boiling to become beautiful salt again, white as the snows of December. There are other minerals besides salt in the beds in the mountains, and, being soluble in water, they also come down the tiny railroad with musical laughter. How can we separate them, so that the salt shall be pure for our tables? The other minerals are less avaricious of water than salt, so they are precipitated, or become solid, sooner than salt does. Hence with nice care the other minerals can be left solid on the bushes, while the salt brine falls off. Afterward pure water can be turned on and these other minerals can be washed off in a solution of their own. No fairies could work better than those of solution and crystallization. MORE GRAVITATION At Hutchinson, Kan., there are great beds of solid rock salt four hundred feet below the surface. Men want to get and use two thousand barrels a day. How shall they get it to the top of the ground? They might dig a great well--or, as the miners say, sink a shaft--pump out the water, go down and blast out the salt, and laboriously haul it up in defiance of gravitation. No; that is too hard. Better ask this strong gravitation to bring it up.