Explaining Earthquakes ca. 1500
Posted by Darin Hayton on 02/20 at 10:55 PM
In early modern Europe natural phenomena fell broadly into two categories: unpredictable and therefore prodigious or predictable and remarkable. Both types of phenomena were often laden with meaning and subject to multiple interpretations. The more unusual the phenomena the more pregnant with significance and meaning. Eclipses and planetary conjunctions were the most common predictable natural phenomena. They were the subject of endless and often competing interpretations, usually published in the cheap annual prognostications that flowed from the presses in early modern Europe.
These prognostications were usually printed simultaneously in Latin and the local vernacular, and often pirated copies were printed in neighboring cities.
Whereas eclipses were relatively common and predictable, comets were reasonably common but unpredictable. Consequently, judgements on comets were always after the fact, offering interpretations of what the comet signified or caused. Comets were almost always harbingers of death, destruction, famine, wars, and general doom. Occasionally an author would find something positive to say, usually in predicting the demise of his patron’s enemy, as Martin Bylica did in his judgement on comet of 1472. Bylica was the court astrologer for the Hungarian king Matthias Corvinus. In his previous judgement, on the comet of 1468, he had hinted at the death of Corvinus’s enemies in Bohemia. By 1472 these enemies had died, a fact that Martin Bylica claimed he had predicted. Bylica interpreted the latest comet as an indication that Corvinus’s latest foe, the Holy Roman Emperor Frederick III, was in danger of losing both battles to Corvinus and possibly his life. But in both cases Bylica warned his patron Corvinus to be careful, that these comets suggested considerable bloodshed even in Hungary and possible danger for the king himself.
Both types of texts circulated in large numbers well before the advent of print. With the spread of printing especially in the Germanies, these astrological judgements proliferated wildly.
Earthquakes formed another natural phenomenon that various authors linked either to comets or to eclipses. Like comets, earthquakes were unpredictable and prodigious. And like comets, they usually indicated death, decay, and destruction.
Earthquakes were commonly associated with comets. Throughout the middle ages, authors referred to Aristotle’s Meteorology when they claimed that comets often preceded comets. They are ambiguous about whether or not comets cause earthquakes or if the two phenomena share a common cause. So, when Aegidius of Lessines wrote his judgement on the comet of 1264, he said in one passage that earthquakes occur after comets. Then, in another passage, he pointed out that what causes comets also causes violent winds. These winds, in turn, seem to cause earthquakes. The connection between dry, hot, violent winds and earthquakes was common. Peter of Limoges made similar claims in his judgement on the comet of 1299, as did the anonymous author of the judgement on the comet in 1301. A fuller explanation can be found in John of Legnano’s judgement on the comet of 1368. He cites Aristotle and Seneca as evidence that earthquakes follow comets. The reason, he claims, is because the inflammable vapors that are drawn up into the upper atmosphere that the sun ignites into comets comes from within the earth. The vapors are initially blocked by the cooler surface. When they escape through the surface, they disrupting parts of the surface and cause earthquakes.
It was precisely this explanation of inflammable vapors escaping from within the earth that contributed to the association between earthquakes and pestilences. Contemporary responses to the plague in 1348 often made this connection explicit. The Medical Faculty at the University of Paris associated earthquakes with comets, and claimed that they were signs of plague. Alfonso of Córdoba likewise attributed the plague to earthquakes. The vapors that escaped from the interior of the earth putrified and poisoned the air, causing outbreaks of plague. The Italian physician Giorlamo Fracastoro associated earthquakes with plagues.
Earthquakes were also associated with planetary conjunctions. At the end of the fifteenth century the German astrologer Joseph Grünpeck wrote two short tracts on the advent of the French Disease, which we typically equate with syphilis.
He explained that the conjunction of Saturn and Jupiter in the sign of Scorpio in 1484 followed by an eclipse had caused first famines, then earthquakes, and finally the French Disease. More general predictions of doom and gloom preceded the impressive conjunction of planets in 1524, all in the sign of Pisces. Along with floods of Biblical proportions, a number of authors predicted earthquakes. These were, however, vague predictions of destruction rather than specific predictions.
A more interesting and specific explanation comes from the lectures of Georg Tannstetter, a master at the University of Vienna and Leibarts to Emperor Maximilian I. Apparently, Tannstetter tried to explain an earthquake that occurred on 6 April 1511 at 3.1 He claimed that this earthquake was going to be particularly deadly because Saturn was in Libra, where it is in exaltation and consequently particularly powerful. Saturn is, of course, a malefic planet often associated with death and destruction. Moreover, a conjunction between the sun and Venus in Aries, along with an opposition of Saturn and Mercury further confirmed the destructive results of this earthquake. Tannstetter included a brief explanation of the causes—hot vapors escaping from within the earth. He concluded by pointing out that these vapors would putrefy and infect the air making it poisonous, almost certainly leading to outbreaks of disease.
Tannstetter’s brief explanation is particularly interesting for what it suggests about the role of astrology and the content of astrological lectures at the university. Tannstetter is trying to offer a concrete explanation, invoking causes—based on widely accepted ideas about planetary qualities and astrological causation—and drawing from them the logical results. These astrological causes and their results could account for both the physical earthquake and the death and diseases that were thought to follow such events. Astrology was anything but irrational. Further, these notes suggest that Tannstetter’s lectures at the university included explanations of earthquakes as part of his courses on astrology. It would be fascinating to know what other specific topics Tannstetter covered in his lectures. Unfortunately, although the person who copied these note clearly respected Tannstetter, referring to him as the “remarkable master Tannstetter,” the notes end abruptly. There is no clear indication of when they were copied, when Tannstetter held these lectures, or what other topics he covered during that course.
1Tannstetter’s explanation is recorded on the bottom of two folia in a manuscript in the Bayerische Staatsbibliothek, Clm 19690.⇑