The libri fulgurales and the Etruscan doctrine of lightning

No natural phenomenon impressed the ancients as much as lightning. The Etruscans made it the subject of a genuine science, collected in the libri fulgurales. For them a flash of lightning was not a random event but a message hurled by a deity with a precise intention. Understanding which region of the sky it came from, where it fell and what it struck made it possible to grasp the content of that message and to respond to it.

The sky divided into sixteen parts

Pliny the Elder, in the second book of the Natural History, explains that the Etruscans divided the sky into sixteen regions. The observer oriented himself by the cardinal points, and each sector had a different value. The eastern regions were held to be more favourable, the western ones less so; the most dreaded were those that turn from the north towards the west. The same sixteen-part scheme appears on the rim of the bronze liver of Piacenza.

Again according to Pliny, the Etruscan books taught that nine deities had the power to hurl thunderbolts and that there were eleven kinds of lightning. Jupiter, the Etruscan Tinia, had three at his disposal. This plurality distinguished the Etruscan doctrine from the Roman one, which according to the same author kept only two kinds of lightning, attributing those by day to Jupiter and those by night to Summanus, an obscure and very ancient deity.

The three bolts of Tinia

Seneca, in the Naturales quaestiones, describes the three thunderbolts of Jupiter. The first, which the god throws on his own initiative, is a warning and does little harm. The second can be hurled only with the consent of a council of twelve gods. The third, the most destructive, requires the opinion of higher and hidden deities, whom the Romans called dii involuti. Even the king of the gods, then, was not free to act alone.

Seneca also reports a classification attributed to Aulus Caecina, an Etruscan friend of Cicero. Lightning was distinguished according to the moment at which it fell: some bolts preceded a decision and served as advice, others followed it and confirmed or condemned its outcome, and still others struck a person who was doing nothing at that moment and announced something about his condition.

The place that was struck

The spot where lightning had fallen became sacred. The traces of the heavenly fire were gathered and buried, and the place was fenced off so that no one would set foot there. In the Roman world these enclosures were called bidentalia, perhaps from the name of the sheep sacrificed to purify them. Latin inscriptions bearing the formula fulgur conditum, meaning buried lightning, have been found at various places in Italy and mark precisely these forbidden spaces.

A remarkable document linked to this tradition is the brontoscopic calendar handed down in Greek by John Lydus, a Byzantine official of the sixth century. The text, which Lydus presents as derived from a translation by Nigidius Figulus, gives for each day of the year the meaning of a thunderclap. It is hard to say how much of the original doctrine it preserves, but it shows the long fortune of this knowledge.

The doctrine of lightning was perhaps the most enduring part of the Etrusca disciplina. As late as the fourth century AD a law of Constantine allowed haruspices to be consulted when lightning struck the imperial palace or a public building. For the Etruscans the sky was a text written in fire, and its reading remained in the hands of specialists until the last days of paganism.