"Photographing the Dark: Nadar’s Descent into the Paris Catacombs", @AllisonCMeier on Nadar’s determined efforts (involving Bunsen batteries, mannequins, and a good deal of patience) to document the beauty and terror of this realm of the dead: https://publicdomainreview.org/essay/photographing-the-dark-nadars-descent-into-the-paris-catacombs