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." [Illustration: AN ANXIOUS MOMENT--LOOKING FOR THE YELLOW STREAK From photograph by C. C. Pierce & Co.]