In the early days of mining in this country it was in the placer fields that the prospector reaped his fortune. In California, successive ages of erosion had worn away portions of the gold-bearing veins of the Sierras, and the rains and brooks and rivers had distributed the metal along the valleys and plains where it but awaited the test of the pan to disclose its whereabouts. In ten years after the prospector began his wanderings through the State there were taken from the placer diggings more than $500,000,000 worth of gold. In the year 1875, $20,000,000 worth were washed from the sands of California Gulch alone.
When the placer fields were practically worked out the prospector began looking for "mother lodes," as they termed the veins which had furnished the dust and yellow lumps they had been gathering from the sands in the placer diggings. In this search the real skill of the prospector comes into play.
Gold is found in a variety of rocks. Its usual home, however, is in quartz, although a few of our richest mines have been found in other rocks. The prospector must be able to read the book of nature closely.
He starts from the placer fields to search for the mother lode. He must determine in what direction to prosecute his search. The fine particles of gold which have been disseminated through the soil must originally have come from higher ground. One thing to determine is whether, since the gold has been laid down, there has been displacement or upheaval. If not, it is evident that somewhere upstream he must look for the vein, but the question is: Where. There are mountains and valleys upon every side, and in any one of these may lie the object of his search.
He circles about, looking for "float," as the small pieces of disintegrated quartz or rock are called. If he finds one piece he seeks a second and a third, that he may get a line or trail to the point from which they came.
We will suppose that he finds several pieces of float at intervals on a certain line. He follows these to a point where two cañons or valleys join. Here is another puzzle. He must again turn to the book of nature and closely scan her pages. His mode of reasoning will be something like this:
"Here are three pieces of float. One I found back at the mouth of this valley. Another I picked up forty rods back, and here, where the cañon splits, I find the third. Now from which branch did they come? They could not have come from the sides of this cañon, for they bear away from both sides where I found this last piece. Now, if they had come from the left branch they would have landed over against the right side of the valley, for there is where the débris from that gulch has piled up. The float was on the left side and therefore must have come from the gulch on the right. They did not come from far, for the edges have not been worn smooth by the action of the water and by friction with other pebbles. Then, too, this last piece is too large to have been carried any great distance."
