The long car carried the men down into the depths of the Empire Gold Mine outside of Grass Valley, California. The year is 1850. These men are working to find and extract gold from the hard quartz rock in the Foothill Mountains of California. The tunnel that they were descending down wasn't very high, so they had to watch their heads. There they were, a line of men, one seated behind the other, moving slowly down a track. One half mile (about 2500...