Horace Carver Hovey, Hovey's Handbook of the Mammoth Cave of Kentucky
“ The ceiling is coated with manganese dioxide, and through this black background emerge hundreds of brilliant white stars, made by the efflorescence of the sulphate of magnesia. These are invisible at first, and the magnificent archway sweeps above us in midnight blackness. Long benches are ranged against the right-hand wall, on which the guide seats us, while he collects our lamps and vanishes with them behind a jutting rock. Then comes the marvelous illusion. The roof seems lifted to an immense height. Indeed, we seem to gaze from a cañon directly up to the starry sky. ”
