Europeans apparently produced nine or ten times as much copper and silver in the first century CE as in the thirteenth century CE, with all the energy demands that implies—people to dig the mines, and animals to cart away the slag; more of both to build roads and ports, to load and unload ships, and carry metals to cities; watermills to crush the ores; and above all wood, as timber to shore up mineshafts and fuel to feed forges. This
