Several such vats were being worked at any one time. Enoch explained to Jack that the amalgam had to be mixed for twenty-four hours. Then the vat was upended to make a heap of the stuff on the ground. At this particular mine, there were dozens of such heaps arrayed across the meadow, each one protected from the rain by a canopy of rugged cloth, and each stuck with a little sign scrawled with information about how long it had been sitting there. 'This one was last worked ten days ago – it is due,' Enoch told him, reading one of the signs. Indeed, later some of the workers rolled an empty tub up to that pile, shoveled the amalgam into it, added water, and began to work it with their feet again.