Inside the Milberg Gallery: Alchemical Eruptions

The following is the first in a series of inside looks at the current exhibition in Princeton University Library’s Ellen and Leonard Milberg Gallery at Firestone Library, “Through a Glass Darkly: Alchemy and the Ripley Scrolls 1400-1700.”

Curated by Jennifer M. Rampling, Associate Professor of History at Princeton University, the exhibition shows how European alchemists built on Greco-Egyptian, Islamic, and late medieval foundations to create a golden age of alchemy from the 15th century to the time of Sir Isaac Newton.

Alchemical Eruptions 

Mundus subterraneus, in XII libros digestus (1665)

In seventeenth-century Italy, the trembling earth invoked both terror and opportunity. No-one knew this better than Athanasius Kircher (1602-1680), a Jesuit professor at the Roman College. In 1638, he climbed down into the crater of Mount Vesuvius to divine the secrets of the earth. In a later treatise, the "Mundus Subterraneus" (1665) or “Subterranean Earth,” he gives us a taste of his literary self-portrayal—beginning with his heroic descent into the volcano as the fiery fumes start to rise and envelop him.1

Volcanic fumes rise in the Phlegraean fields (near Naples), Mundus Subterraneus

Mundus Subterraneus (1665): Volcanic fumes rise in the Phlegraean fields (near Naples), Rare Books Division, Department of Special Collections, Princeton University Library.


One of the most seismically active countries in Europe, Italy was continually plagued by earthquakes and volcanic activity. Like others, Kircher interpreted these disasters as signs of God’s wrath, but his deeper interests lay in the natural causes of these phenomena. His "Mundus" was a work of natural philosophy in two volumes, each made up of 12 books, and each book dealing with an earth-related topic: the formation of valleys and mountains, the origins of lakes and rivers, the growth of minerals and metals, the nature of fossils, as well as the causes of earthquakes and volcanic eruptions.

What is less-known about Kircher’s "Mundus" is that it also included a book on alchemy, which is currently on display in Princeton University Library's "Through a Glass Darkly" exhibition.

Why alchemy? Kircher’s inclusion of alchemy, the pre-modern art of experimenting with matter through chemical means, signaled his desire to engage a field of ambiguous reputation for his earth-related studies. It is striking that Kircher’s vision of the earth—as a subterranean network of passages heated by a “central fire” (ignis centralis)—worked as a simile for a planet-sized alchemical furnace.

Central fire heats the subterranean passages in the earth from Mundus Subterraneus

Mundus Subterraneus (1665): The central fire heats the subterranean passages in the earth, Rare Books Division, Department of Special Collections, Princeton University Library.


In Kircher’s words, the passageways inside the earth comprised “innumerable furnaces and vessels” in which natural substances “dissolved,” “calcinated,” “coagulated,” “putrefied,” and “fermented.”2 The operations continually taking place within the earth were here clearly described using the vocabulary of alchemy; it would be a mistake to view these as mere metaphors.

In his chapter on “furnaces, vessels, degrees of heat, and other chymical operations”, Kircher elaborated on his interest in alchemical practices.3 Building on medieval and Paracelsian alchemy, Kircher laid out how mixing together mercury, sulfur, and salt within a furnace would yield diverse metals which could also be found inside the earth. Moreover, he explored how alchemical distillation created vapors, fumes, and other types of exhalations that were associated with the earth.4

Alchemical furnaces image from Mundus Subterraneus

Mundus Subterraneus (1665): Alchemical furnaces, Rare Books Division, Department of Special Collections, Princeton University Library.


Kircher’s relationship to alchemy has left scholars puzzled.5 To be sure, he attacked as potentially demonic the process of transmutation—the procedure by which alchemists attempted to convert base metals into gold.  However, Kircher was sympathetic to other aspects of alchemy. For example, he praised the role of alchemical distillation in the preparation of remedies and his vision of the Earth’s formation drew heavily on concepts within Paracelsian alchemy.6

Kircher’s interest in alchemy also helped him to make sense of volcanoes. What kind of process was a volcanic eruption? This was a question Kircher answered by drawing on alchemy. When he climbed into the fuming crater of Mount Vesuvius, he recalled smelling the “intolerable stench of sulfur and burning bitumen” (intolerabili sulphuris et bituminis ardentis mephiti).7 When Vesuvius finally erupted, he described the ensuing process as a series of alchemical transformations:

  • The bubbling-up of molten minerals created a new mountain, as it were, by flowing into all parts of the surrounding area. Through the ingenious brush of nature, the mountain first turned green from copper; then yellow from sulfur, arsenic, and sandarac; then red from cinnabar and minium; then black from vitriol mixed with water …8

Kircher had recreated the outpouring of molten rock by breaking it down into its alchemical constituents.

Finally, Kircher took an interest in the history of alchemy. As the “Through A Glass Darkly” exhibition illustrates, alchemists were trying to establish the origins of their practices. Kircher denied the claim by some that the father of alchemy was the biblical Adam, an honor usually reserved for astronomy. Instead, Kircher traced the name of the discipline, Al-Chimia in Arabic, back to Chami (Ham), the son of Noah who repopulated Egypt after the great Flood.9 For Kircher, this piece of etymological evidence was sufficient to show that the ancient Egyptians had practiced alchemy. Yet he complained that many ancient authors made no mention of alchemy in their writings. Finding only textual scraps, Kircher relayed individual anecdotes, for example the Roman emperor Caligula attempting to turn orpiment (a yellowish mineral) into gold by boiling it. For Kircher, alchemy was mainly a product of medieval practitioners—Arnaldus de Villa Nova, Raymond Lull, and others—who had substantiated it into an art.10

While Kircher has often been portrayed as a critic of alchemy, his "Mundus Subterraneus" incorporated a variety of traditions, mixing medieval alchemy with Aristotelian natural philosophy. The resulting amalgam of traditions embodies the kind of syncretism that is so hard for historians to capture. In Kircher’s work, alchemy intermingles with many forms of natural knowledge, dissolving into the overall mixture, yet at times bubbling up again at the surface.

Discover more about "Through a Glass Darkly" exhibition through PUL's online exhibition.

Read more about other objects in the exhibit through the Inside the Milberg Gallery series.

The exhibition will run from April 6 through July 17, 2022. It is open daily from noon to 6 p.m. All visitors must sign-in and attest to being fully up-to-date with COVID-19 vaccinations.

Published April 20, 2022

Written by: Jeremy Robin Schneider. Jeremy Robin Schneider is a Ph.D. candidate in history of science at Princeton University. His dissertation is a history of fossil ammonites from the sixteenth through the nineteenth centuries, tracing how an odd assortment of “stones” were turned into the remains of a lost world, absent from written records and vanished off the face of the earth.

Media Contact: Barbara Valenza, Director of Library Communications


1Paula Findlen (ed.) Athanasius Kircher: The Last Man Who Knew Everything, Routledge: New York and London 2004, 20-21.
2Athanasius Kircher, Mundus Subterraneus, vol. 2, Jan Janssonius and Elizeus Weyerstraten: Amsterdam 1665, 236.
3Athanasius Kircher, Mundus Subterraneus, vol. 2, Jan Janssonius and Elizeus Weyerstraten: Amsterdam 1665, 239-250.
4For context, see John Norris, “The Mineral Exhalation Theory of Metallogenesis in Pre-Modern Mineral Science”, Ambix 53, 1 (2006), 43-65 and Anna Marie Roos, The Salt of the Earth: Natural Philosophy, Medicine, and Chymistry in England, 1650-1750, Brill: Leiden 2007: 47-107.
5See e.g. Martha Baldwin, “Alchemy and the Society of Jesus in the Seventeenth Century: Strange Bedfellows?”, Ambix 40, 2 (1993), 41-64.
6Athanasius Kircher, Mundus Subterraneus, vol. 2, Jan Janssonius and Elizeus Weyerstraten: Amsterdam 1665, 390-408; Hiro Hirai, “Athanasius Kircher’s Chymical Interpretation of the Creation and Spontaneous Generation,” in: Lawrence M. Principe (ed.), Chymists and Chymistry: Studies in the History of Alchemy and Early Modern Chemistry, Science History Publications: New York 2007, 77-87.
7Athanasius Kircher, Mundus Subterraneus, vol. 1, Jan Janssonius and Elizeus Weyerstraten: Amsterdam 1665, “Praefatio” [5r].
8Ibid., “Praefatio” [5v]: “Materia que ex centro montis continuo eructabatur, novum veluti montem efficiebat, mira striarum varietate praeditum, quam varia mineralium liquefactorum ebullitio in omnes circumferentiae partes fluxu suo, coloreque nunc viridi ex aere, modo fulvo ex sulphure, arsenico et sandaraca, iam rubro ex cinnabrio minioque, iam nigro, ex vitriolo aquis mixto, vel ex ipsis cineribus cineritio, ingenioso Naturae penicillo efformabat.”
9Athanasius Kircher, Mundus Subterraneus, vol. 2, Jan Janssonius and Elizeus Weyerstraten: Amsterdam 1665, 232.
10Athanasius Kircher, Mundus Subterraneus, vol. 2, Jan Janssonius and Elizeus Weyerstraten: Amsterdam 1665, 234-236.