Cave of Dogs

The Cave of Dogs (in Italian Grotta del Cane, literally "Cave of the Dog"[1][2]) is a small cave on the eastern side of the Phlegraean Fields near Pozzuoli, Naples.[3] Inside the cave is a fumarole that releases carbon dioxide of volcanic origin. It was a famous, if gruesome, tourist attraction for travellers on the Grand Tour. The carbon dioxide gas, being denser than air, tends to accumulate in the deeper parts of the cave. Local guides, for a fee, would suspend small animals (usually dogs) inside it until they became unconscious. Because humans inhaled air from a higher level they were not affected. The dogs might be revived by submerging them in the cold waters of the nearby Lake Agnano. Tourists who came to see this attraction included Goethe, John Evelyn, Alexandre Dumas père, and Mark Twain. The lake became polluted and it was drained in 1870; the spectacle fell into disuse and the cave was closed. However the area is now being restored by volunteers.[4][5][6][7][8]

The principle of the Cave of Dogs sketched by Alfred Swaine Taylor, 1832
The Cave of Dogs near Puzzuoli, Italy. A guide shows a suffocated dog to a man and woman tourist.
Lake Agnano and the Cave of Dogs in their heyday. Etching by the Sieur de Rogissart, 1706.

The cave was often described in nineteenth century science textbooks to illustrate the density and toxicity of carbon dioxide,[9] and its reputation has given rise to a popular scientific demonstration of the same name. Stepped candles are successively extinguished by tipping carbon dioxide into a transparent container.

The cave was recently investigated by Italian speleologists, including Rosario Varriale, who interpreted it as a man-made cavity constructed in antiquity, possibly as a sudatorium. The carbon dioxide level was measured at 9.9%.[10] According to the Australian speleologist Garry K. Smith, a concentration of 5-10% produces in humans “Violent panting and fatigue to the point of exhaustion merely from respiration & severe headache. Prolonged exposure at 5% could result in irreversible effects to health. Prolonged exposure at > 6% could result in unconsciousness and death.”[11]

References
  1. HALLIDAY, William R; ClGNA, Arrigo A (2006). "The Grotta Del Cane (Dog Cave), Naples, Italy" (PDF). CAVE AND KARST SCIENCE , 2006 Transactions of the British Cave Rescarch Association. 33 (3): 37–42.
  2. Urban, Sylvanus (1753). "The Gentleman's Magazine and Historical Chronicle, Volume XXIII. Page 16. "Grotto Del Cane described, with the cause of its effects"".
  3. "Grotta del Cane: Italy". Geographical Names. Retrieved 26 March 2015.
  4. Taylor, Alfred Swaine, An Account of the Grotta del Cane; With Remarks Upon Suffocation by Carbonic Acid, The London Medical and Physical Journal, 1832, 278-285.
  5. Fleming & Johnson, Toxic Airs: Body, Place, Planet in Historical Perspective, Pittsburgh, 255-256.
  6. Kroonenberg, Why Hell Stinks of Sulfur: Mythology and Geology of the Underworld, Chicago, 2013, 41-45.
  7. Jeff Matthews, Naples: Life, Death & Miracles: Agnano & the Grotto of the Dog. Archived 2016-12-20 at the Wayback Machine, visited 26.3.2015. "The area degraded terribly after WWII and became an eyesore from shoddy overbuilding and illegal waste dumping. I drove by the baths hundreds of times over the years and never knew about the lake, never knew that I was 100 yards from the Grotto of the Dog ...".
  8. Grotta del Cane visited 26.3.2015.
  9. The above image is from L'air et le monde aèrien, an 1865 textbook by Arthur Mangin, p.162
  10. Napoli Underground, Grotta del Cane Nuove Ricerche. Archived 2018-02-08 at the Wayback Machine visited 26.3.2015.
  11. Smith, Garry K (1996). "Naked Flame Tests for, and Human Tolerance to, Foul Air in Caves" (PDF). Helicitite. Journal of Australasian Speleological Research. 34 (2): 39–47. ISSN 0017-9973. Retrieved 26 March 2015.

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