A large portion of the salt used in the United States comes directly from rock salt strata, hundreds of feet below the surface of the ground. These were perhaps the bed of the ocean ages and ages ago. There is a great extent of the beds in New York, Michigan, Ohio, Kansas, and other States. In Michigan there is a stratum of rock salt thirty to two hundred and fifty feet thick and some fifteen hundred to two thousand feet below the surface. To mine this would be a difficult and expensive undertaking, and a far better way has been discovered. First, a pipe is forced down through the surface dirt, the limestone, and the shale to the salt stratum. The drill works inside this pipe and bores a hole for a six-inch pipe directly into the salt. A three-inch pipe is let down inside of the six-inch pipe, and water is forced down through the smaller pipe. It dissolves the salt, becomes brine, and rises through the space between the two pipes. It is carried through troughs to some great tanks, and from these it flows into "grain-settlers," then into the "grainers" proper, where the grains of salt settle. At the bottom of the grainers are steam pipes, and these make the brine so hot that before long little crystals of salt are seen floating on the surface of the water. Crystals form much better if the water is perfectly smooth, and to bring this about a very little oil is poured into the grainer. It spreads over the surface in the thinnest film that can be imagined. The water evaporates, and the tiny crystals grow, one joining to another as they do in rock candy. When they become larger, they drop to the bottom of the grainer. They are now swept along in a trough to a "pocket," carried up by an endless chain of buckets, and then wheeled away to the packinghouse. The finest salt is made by using vacuum pans. These are great cans out of which the air is pumped, and into which the brine flows. This brine, heated by steam pipes, begins to boil, and as the steam from it rises, it has to pass through a pipe at the top and is thus carried into a small tank into which cold water is flowing. The cold makes the steam condense into water, which runs off. The condensed water occupies less space than the steam and so maintains the vacuum in the pan. For a perfect vacuum the brine is boiled at less than 100 deg. F., while in an open pan or grainer it requires 226 deg. to boil brine. The brine is soon so rich in salt that tiny crystals begin to form. These are taken out and dried. If you look at some grains of table salt through a magnifying glass, you can see that each grain is a tiny cubical crystal. Sometimes two or three are united, and often the corners are rounded off and worn, but they show plainly that they are little cubes.