Field of Science

Showing posts with label 14th century. Show all posts
Showing posts with label 14th century. Show all posts

Does praying help prevent natural disasters?

Saint Januarius is the patron of Naples and annually a flask of his (supposedly) blood is presented during a public procession in the city. If, so the legend goes, the dry blood becomes liquid again the city will be spared of any disaster and misfortune. It must be said that the supposed premonitory miracle and its interpretation is very complicated. Factors like timing, how much and how the blood liquefies, color and density of the resulting liquid play a role.

Fig.1. The eruption of Vesuvius in 1631, Saint Januarius is shown above the vulcano. He's a silent guardian, a watchful protector.... most of the times.

The first supposed miracle happened in 1389 and in 1924 geologists Giovanni Battista Alfano (1878-1955) and Antonio Amitrano compiled a list, looking on how well the premonitory signs correlates with disasters or the lack of such. In years where the miracle failed to happen Mount Vesuvius erupted eleven times and nineteen earthquakes hit the city. In years when the miracle happened Vesuvius erupted just five times. So it seems that divine protection works half the times. 
Also whenever Vesuvius seems to become active a procession with the relics of the saint is organized to implore divine protection.These processions helped diplomat and amateur vulcanologist Sir William Douglas Hamilton (1730-1803) to reconstruct the activity of Vesuvius in recent history.

Fig.2. "The recent eruption of Vesuvius: scenes of terror and piety in the face of the eruption", by Achille Beltrame (1871-1956), cover of the newspaper "La Domenica del Corriere" April 1906.

Naples is not the only city with a holy protector. In Catania it´s Saint Agata. According to local folklore a veil of the saint has the power to stop a lava flow. During the disastrous eruption of Mount Etna in 1669 Saint Agata was invoked. For a time the lava flows could be diverted by a group of brave men, building dams of lava rocks in front of the advancing flow and digging alternative paths, also the walls of the city of Catania resisted. But finally the lava entered in a breach of the walls, claiming 15.000 victims.


Fig.3. Fresco by painter Giacinto Platania (1612-1691) of the eruption of Mount Etna in 1669, Platania witnessed the eruption himself and the painting is quite realistic, showing the lava flows stopped by the city walls.

Still in 1971 divine protection was claimed for the city of Sant'Alfio, near Catania, and it apparently worked this time. 

As why those inconsistent results over time - as they say the lord works in mysterious ways.

Dante´s Inferno - The Geology of Hell

"Through me the way is to the city dolent;
Through me the way is to eternal dole;
Through me the way among the people lost.
...[]....
Before me there were no created things,
Only eterne, and I eternal last.
All hope abandon, ye who enter in!
"
Canto III


"The Gates of Hell", by Jehan Froissart, 15th century.

For a long time the inner earth was a mysterious place, supposedly the reign of demons and place of eternal damnation. Italian poet Dante Alighieri (1265-1321) imagined an especially elaborate version of hell in the “Divine Comedy”. Like later authors he used in part his contemporary knowledge as inspiration and included in the description of the nine circles of hell, with Lucifer residing in the lowest, real landscapes. Dante mentions earthquakes, rivers, the shape of mountains and landslides, a desert of hot sand and some types of rocks (like the marble of Carrara).
 
The circles gradually become smaller with less circumference, as hell is depicted like an inverted cone in a sphere, protruding towards earth´s core. This image is based on calculations of Greek philosophers (like Eratosthenes of Cyrene, 276-194BC or Claudius Ptolemy, 100-170AD), Dante even gives an exact value of earth´s radius of 3.250 miles (5.230km, actual radius is 6.371km). 

Dante´s Inferno by Jan van der Straet, 1587.

The cone formed when Lucifer, the fallen angel, fell on earth, the impact was so great that it even shaped earth´s surface, with continents formed on the northern hemisphere and the southern hemisphere covered by the sea (Dante didn't know of the existence of the southern continents of Australia and Antarctica). 

"The fallen angels" by Vincent of Beauvais (1463).

In the south we will find only the mountain of Purgatory. Purgatory, together with the holy city of Jerusalem, forms an axis passing earth, with Lucifer´s belly as center of earth. An allegoric image, as Lucifer is damned as far as possible away from the sun and divine light.
 
Illustration to Dante's "The Divine Comedy" from the "Codice Urbinate Latino 365" (1480) showing the frozen center of earth with Lucifer trapped in eternal ice. Dante imagined this part of hell as frozen wasteland, as it was as farest away from the warm sun as possible in his geocentric universe (earth as center of the cosmos, with sun, moon and stars around it).

Dante when entering hell is guided by the shadow of ancient Roman poet Publius Vergilius Maro (70-19BC), better known as Virgil. During his pilgrimage from hell to purgatory and paradise, the way is obstructed by ruins, destroyed, as one demon reveals to Virgil, by an ancient earthquake.

Like the ruins this side of Trent left by the landslide/
an earthquake or erosion must have caused it/
that hit the Adige on its left bank,/
when, form the mountain’s top where the slide began/
to the plain below, the shattered rocks slipped down,/
shaping a path for a difficult descent/
so was the slope of our ravine’s formation.

 
Dante describes in these verses the sight of a 3.000 years old landslide near the Italian city of Trento, even arguing that the cause of this ancient landslide was erosion or an earthquake. Dante maybe visited this site, as he lived for a time in the nearby city of Verona. For sure he used German naturalist Albertus Magnus (1200-1280) as reference, who argued that by the river eroding the base of the mountain it collapsed, forming the ruined landscape of the landslide. Dante also experiences an earthquake at the shores of the river Acheron, caused by winds or vapors blowing inside the caverns of earth and igniting from time to time.

It´s curios to note that Dante didn't describe hell filled by fire, despite Mount Etna and Vesuvius were regarded in ancient times as gates to hell and both mountains seem to be filled by the liquid “lava-fire”.... not to mention hellish volcanic eruptions. However Etna is mentioned when referring to the island of Sicily, as site with sulfur vapors. The Phlegethon and some minor rivers are described as rivers of boiling blood with "lithified" margins, like - so Dante writes - the hot springs of Bullicame near the city of Viterbo in the Lazio region.

The Icelandic volcano Hekla as gateway to hell, from "Historiae de gentibus septentrionalibus" by Olaus Magnus (1490-1557), Archbishop of Uppsala.

There is may a simple explanation why Dante didn't include volcanoes more prominent in his work. Both Etna and Vesuvius were at the time relatively calm (Vesuvius erupted only in 1321-1323) and so of no real interest to the poet.

Geology plays even a role in the punishment of the sinners. In the third circle the simonists (people who sold holy artifacts for profit) are driven upside down into the ground and "squeezed tightly in the fissures of the rock".
 The robbers are punished in a circle filled with poisonous snakes. Dante describes looking down into the pit was he sees:

“Within this cruel and bitterest abundance/
people ran terrified and naked, hopeless/
of finding hiding-holes or heliotrope./
Their hands were tied behind their backs with serpents.”


Heliotrope (a chalcedony variety) was since ancient times a gemstone much valued for its magical properties, like to protect from the venom of snakes. 


After Inferno Dante finally reaches the slopes of Mount Purgatory, leaving hell behind:

"The climb had sapped my last strength when I cried:
“Sweet Father, turn to me: unless you pause/
I shall be left here on the mountainside!”/

He pointed to a ledge a little ahead/
that wound around the whole face of the slope./
“Pull yourself that much higher, my son,” he said./

His words so spurred me that I forced myself/
to push on after him on hands and knees/
until at last my feet were on that shelf."


The poets begin their laborious climb up the Mount of Purgatory, illustration by Gustave Doré (1861).

The Divine Comedy is nowadays appreciated for it´s role in the development of literature and Italian language, but it is also valuable source to better understand the natural sciences and the understanding of earth in the 14th century. 

References:
 
KROONENBERG, S. (2013): Why Hell Stinks of Sulfur: Mythology and Geology of the Underworld. University of Chicago Press: 352
ROMANO, M. (2016): Per tremoto o per sostegno manco”: The Geology of Dante Alighieri’s Inferno. Italian Journal of Geosciences, 135(1): 95-108

On the Art of Mineral Identification

Hardness is an important feature used for mineral identification, but it is not the only one. 

Fig.1. Lecture in mineralogy, from Bartholomäus Anglicus "Über die Eigenschaften der Dinge" (1390-1400), on the Characteristics of Things.
 
May the chemist Torbern Bergmann (1735-1784) was one of the first naturalist to discuss mineral-hardness, however, as he believed that clay is also a mineral, he assumed that hardness was strongly influenced by the humidity of the environment and therefore not very useful. In 1784 the geologist A.G. Werner published his textbook "Von den äußerlichen Kennzeichen der Fossilien" (The external characteristics of fossils; fossils as anything excavated from the ground) introducing six hardness-degrees that could be distinguished with simple tools, like a knife, a file or steel-tools, all things available to miners or amateur rock-hounds. Mineralogist René-Just Haüy (1743-1822) introduced also test-minerals, like calcite (Mohs Hardness 3) and quartz (Mohs Hardness 7) for hardness identification. Finally mineralogist Carl Friedrich Christian Mohs published the modern 10-degrees scale in 1822.
 
 
Fig.2. Hornblende (Moos in Passeier, South Tyrol).

The streak, the color of the mineral-powder, is mentioned already by Georg Pawer (1494-1555), better known as Georgius Agricola, in his books on mining techniques. Also Werner considers the streak one of the most important features, where Mohs considers both streak as color of the crystal equally important. However it was Werner to introduce a classification scheme for crystal colors, using terms like steel-gray and apple-green to describe the colors of minerals.
Curiously to get the powder the crystal had to be crushed or damaged, only in 1865 streak plates were introduced.
 

Specific weight was used already by Arabic scholars to distinguish gemstones from fake stones.

 
Fig.3. Apatite (Lodner, South Tyrol). 

Also the reactions of minerals with chemical solutions can be very important. A sort of marble was known already as "Bitterspat", "Murakalzit" and "marble tardum" by Carl von Linné (1707-1778). However in 1791 the French naturalist Deodatus Sylvain Guy de Tancrède greatet de Dolomieu (1750-1801) noted that this rock doesn´t react with acid like common limestone and limestone-marble does. He published this observation and later the Irish chemist Richard Kirwan identified and named the new mineral dolomite - a Ca-Mg-carbonate.

Fig.4. Dolomite from the Dolomites, South Tyrol.

Today many other features, like magnetism, luminescence and radioactivity are used to identify minerals. However until the 18th century only some hundred minerals were known, mostly ores or gemstones, and the described identification methods were more than appropriated for everyday use.

Bibliography:

KORTINIG, S. (1988): Der Strich. Der Aufschluss, Jhg. 39: 221-225
KORTINIG, S. (1988): Die Härte der Minerale. Der Aufschluss, Jhg. 39: 371-378
KORTINIG, S. (1988): Die Farbe und der Glanz der Minerale. Der Aufschluss, Jhg. 39: 295-299
KORTINIG, S. (1988): Die Dichte der Minerale. Der Aufschluss, Jhg. 39: 376-378
MÜCKE, A. (1988): Die Seiten für den Anfänger. Der Aufschluss, Jhg. 39: 35-38