Until recently, if you wanted to leaf through Athanasius Kircher’s Mundus Subterraneus, you had to sneak into a university’s rare book collection at night, Wilbur Whateley-style.  Now the complete work, with its many bizarre and fantastic illustrations, is available at the Internet Archive—enjoy. John Glassie has an excellent piece on it at The Public Domain Review:

Just before Robert Hooke’s rightly famous microscopic observations of everything from the “Edges of Rasors” to “Vine mites” appeared in Micrographia in 1665, the insatiably curious and incredibly prolific Jesuit scholar Athanasius Kircher published what is in many ways a more spectacular work. Mundus Subterraneus (Underground World), a two-volume tome of atlas-like dimensions, was intended to lay out “before the eyes of the curious reader all that is rare, exotic, and portentous contained in the fecund womb of (Read more…).” There is an “idea of the earthly sphere that exists in the divine mind,” Kircher proclaimed, and in this book, one of more than thirty on almost as many subjects that he published during his lifetime, he tried to prove that he had grasped it.

As a French writer put it some years later, “it would take a whole journal to indicate everything remarkable in this work.” There were extended treatments on the spontaneous generation of living animals from non-living matter, the unethical means by which alchemists pretended to change base metals into gold, and the apparent tricks of nature we now recognize as fossils. The book included detailed charts of “secret” oceanic motions, or currents, among the first ever published. The author’s more or less correct explanation of how igneous rock is formed was also arguably the first in print. According to one modern scholar, Kircher “understood erosion,” and his entries “on the quality and use of sand” and his “investigations into the tending of fields” had their practical use.

Mundus Subterraneus identified the location of the legendary lost island of Atlantis (something that modern science hasn’t been able to accomplish) as well as the source of the Nile: it started in the “Mountains of the Moon,” then ran northward through “Guix,” “Sorgola,” and “Alata” and on into “Bagamidi” before reaching Ethiopia and Egypt. Kircher offered a lengthy discussion of people who lived in caves (their societies and their economy). He reported on the remains of giants (also mainly cave dwellers) found in the ground. And he went into detail on the kinds of lower animals who belong to the lower world (including dragons).

In short, Mundus Subterraneus covered almost every subject that might relate to the realm of earth, as well as many that wouldn’t seem to, such as the sun and “its special properties, by which it flows into the earthly world” and the “nature of the lunar body and its effects.” These correspondences and influences were nothing new, though perhaps only the always-inclusive Athanasius Kircher would choose to publish a series of moon maps in a book about the world below.

All these other subjects notwithstanding, it was Kircher’s theory about the interior of the earth that captured, or at least deserved, the most attention. As he explained, “the whole Earth is not solid but everywhere gaping, and hollowed with empty rooms and spaces, and hidden burrows.” Deep down, it holds many great oceans and fires, interconnected by a system of passageways that reached all the way to its core. In his view, volcanoes, however awful and awe-inspiring, “are nothing but the vent-holes, or breath-pipes of Nature,” and earthquakes are merely the “proper effects of subterrestrial cumbustions” that are sure to go on constantly. The “prodigious volcanoes and fire-vomiting mountains visible in the external surface of the earth do sufficiently demonstrate it to be full of invisible and underground fires,” he wrote. “For wherever there is a volcano, there also is a conservatory or storehouse of fire under it…. And these fires argue for deeper treasuries and storehouses of fire, in the very heart and inward bowels of the Earth.”

According to Kircher, “the fire and water sweetly conspire together in mutual service.” The tides, caused by the nitrous effluvia of the moon, push “an immense bulk of water” through “hidden and occult passages at the bottom of the Ocean” and thrust it “forcibly into the intimate bowels of the Earth.” The resulting winds “excite and stir up” and otherwise feed the subterraneous fire like a huge bellows. The seas, which would stagnate and freeze without the fires, keep the fires from getting out of hand, preventing “unlimited eruptions,” which would “soon turn all to ruins.” The “secret make-up of the mountains” is that they are hollow and serve as reservoirs. Hot baths, hot springs, and fountains are produced where underground water passageways come near or interconnect with the fire channels.

[More at The Public Domain Review]