Two weeks ago, I have presented this poster on the early theories on tornado formation at the 8th European Conference on Severe Storms. The poster shows the major contributors, from Aristotle to Peltier, and their theories on the formation of tornadoes. Given the size of the poster, I was not able to include all the contributions. There is one contribution in particular which I think deserves more attention - "On the violence of the tornado, and the storm", Book 1, Chapter XI from Historiade Gentibus Septentrionalibus (History of the Nordic People) by Olaus Magnus.
Olaus Magnus (or, Olof Månsson) a Swedish ecclesiastic, historian and geographer, was born at Linköping in 1490. In 1510 he began his ecclesiastic studies in Germany and returned to Sweden in 1517. Like his elder brother, Johannes Magnus, Olaus obtained several ecclesiastical positions, as canon at Uppsala and Linköping, and then as archdeacon of Strängnäs. In 1523, King Gustave I appointed Johannes Magnus as Archbishop of Uppsala. After Gustav I's breaking with the Catholic Church, Johannes accompanied by Olaus as his secretary went to Rome in 1537. Johannes died in 1544, and Olaus was appointed as his successor in Uppsala. This was nothing more than a title since by this time Sweden was not Catholic anymore. Olaus spend the rest of his life in Italy, for the most part in Rome were he died in 1558.
Olaus Magnus is mainly remembered today for his History of the Northern People printed in Rome in 1555. The History, one of the first works about the Sweden and its inhabitants, also depicts the history and folklore of other north European countries. The History is divided into 22 books and 476 chapters illustrated with 353 woodcuts.
Another work by Olaus Magnus to which many illustrations from the History refer to is the Carta Marina. Drawn by Olaus between 1529–1539, this is a stunningly detailed map and one of the earlies maps of the Nordic countries. The map also contains a very accurate depiction of the oceanic currents between the Iceland and Faroe Islands. Rossby and Miller (2003) argued that whorls drawn in the ocean by Olaus are to deliberate to be purely artistic expression. Instead, they are representations of the Iceland-Faroe front, that "separates the warm waters flowing north between Iceland and Faroes from the cold waters flowing east east and south around the northern coast of Iceland" (Rosbby and Miller, 2003, p. 87).
Let's now return to Chapter 11 (Books 1) "On the violence of the tornado, and the storm" from the History. As the title indicates, this chapter is devoted to the effects of tornadoes and storms in general. The illustration accompanying the chapter shows a tornado (turbo, in the original Latin text) uprooting trees and lifting the roofs of a church and a house.
Here is the translation form Latin by Cassia Price of the chapter.
In his explanations of the origin of tornadoes, Olaus relies on two theories. In the first theory, proposed by Isidore of Seville (c. 560–636), "the last scholar of the ancient world" and the patron saint of the Internet, tornadoes are produced by the "twisting of winds" (I would discuss Isidore's theory in more details in the next blog post). The second theory in which the tornado "brings about even more winds from the struggle with itself" is attributed by Olaus to Seneca (c. 4 BC–AD 65). As far as I am aware this theory was first proposed by Aristotle (384–322 BC), who stated that tornadoes are produced by the winds trapped in the cloud, spinning around trying to get out and producing cone or column shaped clouds (see Theory 2 in the above poster). After discussing their origin, Olaus describes the characteristics tornadoes. Tornadoes are "round while the wheeling column spins itself", their motions is "wandering, dividing, swirling", they have short life time ("no one has seen a tornado for a full day, not even for an hour") and their "speed is extraordinary". The chapter ends with descriptions the effects of tornadoes: "huge stones have been rolled along from the windmill" by tornadoes, also "from men it my snatch weapons and clothing, whereas from a horse it might steal their rider by [their] force". Thus, as in the case of the Carta Marina, Olaus provides in this chapter from the History stunning details of tornadoes and their effects. Not only this, but in Chapter 35 (Book 1) "On the Signification of Thunderstorms for Every Specific Month" Olaus describes the annual cycle of thunderstorms over Sweden.
In this early "infographic", the year is symbolized by the ribbon. On the ribbon the month are represented by letters i) the summer months: - A-Aprilis, M-Maius, I-Iunius, I-Iulius, A-Augustus, and S-September (upper part of the ribbon) and ii) the winter months: O-October, N-November, D-December, I-Ianuaris, F-Februarius and M-Martius (lower part of the ribbon). The summer months are associated with more rain (upper part of the figure) and lightning (the emerging branches from the letters representing the months, with more branches indicating more frequent thunderstorms). The winter months are associated with more snow (lower part of the figure). This annual cycle, shows that thunderstorms occur all year round in Sweden, with a maximum between May and August. This is consistent with the annual cycle of tornadoes in Sweden, with tornadoes reported in almost every month in Sweden and a maximum between June and August (see Fig. 5 from this paper).