The smoke from cane torches rose to the ceiling of cave passages and, in passages where air circulation was limited, left deposits.

Some passages in Mammoth Cave have ceiling areas blackened by centuries of accumulated torch smoke — not from a single trip or a handful of visits, but from the repeated passage of miners over generations, each carrying fire, leaving the residue of their passage on the limestone above.

These smoke deposits are themselves a form of evidence: they mark the ancient routes.

Passages where the ceiling is blackened were the passages most frequently traveled.