Thousands of years ago, before the time of which we have any history, there were rivers in California, - rivers now dead, - whose sides were steeper and whose channels were wider than those of the rivers in the same part of the world to-day. Rapid streams they were, and busy, too; washing away from the rocks along their sides the gold held there, dropping the yellow grains down into the gravelly beds below. After a time there came down upon these rivers a volcanic outflow; great quantities of ashes, streams of lava and cement, burying them hundreds of feet deep, until over them mountain ridges extended for miles and miles.
Other changes in the earth's surface took place, and in the course of time our streams of to-day were formed. As they cut their way through the mountain ranges, some of them crossed the channels of old dead rivers, and finding the gold hidden there, carried some of it along, rolling it over and over, mixed with sand and gravel, down into the lower lands under the bright sunlight. Here it was found by Marshall and the gold hunters who followed him. These were the placer mines of which we read in Chapter VII.
Gradually the best placer mines were taken up and the newcomers to the gold fields traced the precious metal up the streams into the gravel of the hillsides. Then was begun hydraulic mining, where water did the work. In the canons great dams were constructed to catch the flow from the melting snows of the mountains, and miles of flumes were built to carry the water to the mining grounds. Immense pipes were laid and altogether millions of dollars were invested in hydraulic mining. The water coming down under heavy pressure from the mountain reservoirs passed through giant hose which would carry a hundred miner's inches, and, striking the mountain side with terrific force, washed away the earth from the rocks. Down fell the sand and gravel into sluices or boxes of running water where cleats and other arrangements caught and held the gold, which was heavy, while the lighter mixture was carried out into the canyon.
The material thus dumped on the mountain side was called debris, and to any one living in the mining region of the state that word means trouble - means fighting, lawsuits, ruin. For the debris did not stay up in the canyon, but was washed down into the rivers, overflowing farm lands, spoiling crops and orchards, and making the streams shallow, their waters muddy. So great was the destruction this process caused that, in 1893, the Congress of the United States enacted a law which provided for the creation of a Debris Commission to regulate the business of hydraulic mining in California. The result of the investigations of this commission was to put a stop to all hydraulic mining in territory drained by the San Joaquin and Sacramento rivers, or any other territory where the use of this form of mining should injure the river systems or lands adjacent. Thus, almost in a moment, the important industry was stopped.
It is estimated that over one hundred million dollars were invested in hydraulic mining. Much of this was entirely lost, as the expensive machinery rusted and the water system fell into ruins. It was very hard for the miners, as well as for the commerce of the state, but the act of the government was based upon the principle that one man's business must not damage another man's property. Clever engineers in the pay of the government are still trying to find some way by which the debris can be safely disposed of in order that this valuable system may resume operation.
Deprived of the use of water as their agent, gold hunters next tried mining by drifts; that is, by tunneling into the mountain's side until the bed of a buried river is reached. These tunnels are often five thousand to eight thousand feet long. The gold is brought out of the ground before it is washed clean of the gravel. Sometimes it is mixed with cement, when it has to be crushed in rollers before it can be cleared of other material. The counties where drift mining is most in operation are Placer, Nevada, and Sierra.
Quartz mining is the most expensive manner of getting out gold, and a great deal of valuable and complicated machinery has been invented for this branch of the business. The quartz mines of California are among the richest in the world, and some of the greatest fortunes of modern times have been made from them.
In a mine of this kind there is generally a shaft, or opening, extending straight down into the earth, from which, at different levels, passageways branch out where the veins of gold are richest. The openings must be timbered to prevent caving in, and there must be pumps to remove the water as well as hoisting works to take out the material. Then on the surface, as near as possible to the mouth of the mine, must be located the quartz mill. When possible, a tunnel is used in this mining, which makes the handling of ore less expensive, for then there need be no hoisting works or pumps, since the tunnel drains itself.
Gold in quartz rock is generally in ledges or veins, one to three feet in width. Digging it out is not very hard, save where there is not enough room to stand upright and use the pick, or when, in a shaft deep in the ground, the heat makes it difficult to work. A California boy at the mines wrote recently: "Mining is not so bad; that is, if I could get along without the occasional whack I bestow upon my left hand. Last week I started a little tunnel and pounded my hand so that it swelled up considerably. Drilling is not hard, and loading is a snap, but it's all interesting work and there is the excitement of seeing what you are going to find next."
When the ore reaches the surface it is sent to the mill, where it is first pulverized, then mixed with a chemical which goes about catching up the grains of gold - arresting and holding them fast. It is quite a long process before the gold is completely separated from all other material and ready for shipment. Often the quartz contains other minerals of value, the separation of which requires much work.