IN DUE TIME M R. T HREADER seizes the cupel with tongs and upends it over the freshly polished scale-pan of the balance. The ingot—an oblate bead—falls out, and spins and buzzes on the pan. Some flecks of burnt bone fall around it; Mr. Threader blows these away and then gives the ingot an exploratory nudge or two with his tweezers, to satisfy himself that no other impurities have stuck to it. When he is certain that there’s nothing on that pan except for pure gold, he places a ten-grain standard weight on the opposite pan. This is not nearly enough to balance the ingot—which is good, as far as it goes—and so, now wielding the ivory-handled tweezers, he adds a one-grain weight. Then a half-grain. The scale has gone into motion but still inclines toward the ingot of gold. Mr. Threader is working now with standard weights so small that Daniel can hardly see them: they are evanescent squares of gold foil stamped with fractions. He makes a messy pile of them and then stops, stumped. He removes a lot of small ones and replaces them with a larger one, and hems and haws. Finally he removes every single one of the standard weights, sets them back in their niches in the case, and puts on the single twelve-grain weight that he used earlier to weigh the sample of guinea fragments.