You are mistaken. Romans had been on industrial scale mining copper, gold and silver in Spain and other places. That required unbelievable amounts of energy - m

You are mistaken. Romans had been on industrial scale mining copper, gold and silver in Spain and other places. That required unbelievable amounts of energy - mostly charcoal. Romand knew waterwheel as a source of energy but rarely used - compared to medieval Europe. https://en.wikipedia.org/wiki/Roman_metallurgy#Output https://en.wikipedia.org/wiki/Roman_metallurgy#Output