42 stereoviews on cardstock mounts (overall good to very good condition, several with rich tonality, some with soiling; corner and edge wear to mounts). Rectos with series title, "Magnesium Light Views in Mammoth Cave" and 1866 copyright of Proctor & O'Shaughnessy. Versos with applied paper label including credit to Charles Waldack, photographer, and E. & H.T. Anthony, publishers, as well as image number and title. 

A rare set of stereoviews representing the earliest documented images of Mammoth Cave, Kentucky, and including the first underground photographs taken in America. Through the use of magnesium, Charles Waldack was able to capture the geological and biological features of the longest known cave system in the world.

The set is highlighted by No. 4. Out for the Last Time, described on verso as "a picture of the gentlemen who conceived and executed the project of Photographing the cave, with the reflectors..." The group of three men, which almost certainly includes Waldack, are seated together, surrounded by equipment, including a camera with tripod.

Additional images of note include: Beyond the "Bridge of Sighs," which shows "two 'guides,' just having crossed the bridge towards 'Reveler's Hall.'" -- "Deserted Chamber," featuring a guide entering the chamber from the narrow passage beneath the "Giant's Coffin." -- "Bacon Chamber." -- "Devil's Arm Chair." -- "Scotchman's Trap." -- Dining in "Great Relief." An image capturing a group of guides dining together inside the cave. The only view in the set offered here with the "American Views" imprint, lacking credit to Waldack.

Charles Waldack (1828-1882) was a Belgian-born photographer who was active in Cincinnati, Ohio, during the 1850s-1860s. In addition to being the first to photograph Mammoth Cave, Waldack is also thought to have made the first published reference to CDV-sized tintypes / ferrotype cards.