Ben Hains 1889 (copyright) 32 Elbow Crevice [Views of Mammoth Cave and Vicinity]
Stereoview, half Creative Commons - Wikipedia Robert N. Dennis collection of stereoscopic views, MFY Dennis Coll 90-F199 - See also New York Public Library, digital id: G90F199_012F
"These are pronounced the very best specimens of Subterranean Photography yet produced." - Scientific American
