Passages where the ceiling is clean were not on the main routes, or were explored less frequently, or were visited by people who held their torches lower than the ceiling.

The darkness was not an obstacle the ancient miners overcame once and then ignored.

It was the constant physical condition of their underground work.

Every trip, every pass through every passage, every session at a mineral-bearing wall was conducted in the management of light — the constant calculation of how much flame remained, how much farther to go, how much torch was needed to get back.

What Cane Grows Along And What That Required