| Ben Hains 32 Elbow Crevice [Views of Mammoth Cave and Vicinity] 1889 (copyright) 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 LL/36479 "These are pronounced the very best specimens of Subterranean Photography yet produced." - Scientific American
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