"And when you gaze long into an abyss the abyss also gazes into you."
"Beyond Good and Evil", Aphorism 146 (1886) by German philosopher Friedrich Nietzsche (1844–1900)
Since prehistoric times humans ventured into caves, as proved by the discovery of rock art even in remote parts of many European cave systems. In historic times and in many cultures caves became mythological places or passages to the underworld. According to the Maya the karst caves of the Yucatan peninsula were the gates to Xibalba, or the "Place of fear". Also for the ancient Greeks the only access to the reign of the deaths was by cave entrances or sinkholes, presumably guarded by terrible demons.
A first naturalistic approach to caves and the deep underground was attempted during the Renaissance. The great German scholar Athanius Kircher (1602-1680) publishes in his "Mundus Subterraneus" (1665), a textbook on alchemy and geology, the description of large underground rivers and even lakes, feeding superficial springs. However he also notes that these hidden rivers are inhabited by dragons, giants and even unicorns.
In his "Itinera alpina" ("Voyage in the Alps", (1702-1711) the Swiss physician and naturalist Johann Jakob Scheuchzer (1672-1733) explains caves and fissures formed by the selective erosion of rocks by percolating gas and water.
Fig.1. Johann J. Scheuchzer proposes in 1716 the existence of a primitive hydrologic cycle. "Subterranean rivers" flowing in the underground connect superficial lakes with springs. This theory was based on the chemical properties of the spring water, often enriched with chemical elements. The water - so Scheuchzer - dissolves minerals from veins deep within the mountain and transports the elements to the surface.
The association of caves and water seems obvious, as many caves are in fact formed by dissolution of rocks like lime- and dolostone by water. Dana Hunter investigates this fascinating (and sometimes fatal) reaction between rocks and water in her post about karst and sinkholes in Florida.
During the 18th century caves were regarded mostly as curiosities and places for tourists. The serious study of caves came relatively late. One of the first naturalist studying caves in the U.S. was polymath Constantine Samuel Rafinesque-Schmaltz (1783-1840), who published in 1832 a description and classification of the caves of Kentucky. Thomas Jefferson made the first map of a cave in the U.S. (Madison's Cave in Virginia) and in his "Notes on the State of Virginia" (1853) published various other maps of caves.
The demand for nitrates to manufacture gunpowder during the late 19th century and early 20th century was satisfied by the excavation of organic deposits preserved in caves, like Mammoth Cave in Kentucky. In 1878 cave diggers opened a passage into the Luray Caverns (Virginia) and Scientific American commissioned an article about the discovery to clergyman and amateur scientist Horace C. Hovey (1835 - 1913). Based on this and earlier cave explorations Hovey published in 1882 a highly influential book with the title "Celebrated American Caverns". In response to Hovey's stories about cave adventures many show caves were made accessible to the interested public and soon the exploration of the underground became a scientific discipline.
HALLIDAY, W.R. (2006): America, North: History. In GUNN, J. (ed.) "Encyclopedia of caves and karst science": 102-109
ROMERO, A. (2009): Cave Biology - Life in Darkness. Cambridge University Press: 291