Underground Rivers - University of New Mexico

Chapter 9 -- Thermodynamic Engines
Mundus Subterraneus was widely reprinted with altered
graphics, but no matter the particular artist, the
hydrophylacia are central to the composition. Three of the
four illustrations shown here are geographically explicit.
The hydrophylacia model was old, however, even in Kircher's era. Conrad von Megenberg's Das
Buch der Natur (1349-1351), the first illustrated book on nature, included a description of the bigcavity
hydrology.
Some [waters] originate in the big hollow mountain which is cold and rocky. The watery steam
dissolves here into water drops which mix with the soil, with the daily rain and the snow. So the
water drops collect in the cavities and form a rivulet; many rivulets form a big stream which
seeks an exit from the mountain and eventually breaks through. This is the spring of flowing
waters or of a well on the mountain, or a lake on the mountain.
As the hydrophylacia are above sea level, Kircher needed to explain how seawater attained the
elevation. The fact that that temperature increases with depth in dry mines guided his ideas.
The central fire pours out surging and burning exhalations to each and every part by firecarrying
channels. Striking the water-chambers it forms some into hot springs. Some, it
reduces to vapors which, rising to the vaults of hollow caves, are there condensed by cold into
waters which, released at last, give rise to springs and rivers.
An event in 1678 seemed to support the existence of hydrophylacia. Flash flooding of the
Garonne River, which issues from a spring in the Pyrenees, without there having been local
rainfall, was attributed to collapse within the mountain displacing an underground lake.
So this Mass of the Mountain in its settling all at once upon the Water of the Gulphs or
Subterraneous Lakes, which are under the highest Pyrenean Mounts ... do force the Water to
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