Poster presented at the 8th European Conference on Severe Storm, Wiener Neustadt, Austria, 14–18 September 2015. A PDF version of the poster can be found here

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.

The cover of the History of the Northern People (Rome, 1555) courtesy of Google Books.

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.

Woodcut from the chapter "On the violence of tornado, and the storm" from the History of the Nordic People by Olaus Magnus. (source:

 Here is the translation form Latin by Cassia Price of the chapter. 

As all who tell the secrets of nature or who have observed them know, tornadoes, and the storms of Northern places, have awesome and dangerous energy. Especially because of the complex and unfailing cause of their origins, the means for which might be found. Therefore, a tornado (argues Isidore), is the twisting of winds, and this has been said on earth as many times as the wind rouses itself, and the earth is sent into a spin: this tornado brings about even more winds from the struggle with itself (Seneca is a witness of this in his Naturales quaestiones). And these areas are caught up around the earth and brought forth: and for this reason orchards are torn from their roots, and whatever it broods over it strips bare to the ground, and, at the same time, ripping up the trees, and the rooves just lower than the clouds; at any rate nothing is higher. Its shape is round: while the wheeling column spins itself, all the clouds seize it quicker and quicker. And its motion is wandering, dividing, swirling. But then it cannot stay, for it struggles, because it is wandering, inconstant air; at the end however, it moves least of all. And so no storm lasts long. But the commotions of storms, however much more power they might have, the less time they last, having arrived, because when they come to their climax, all the force is diminished, and that excitement is necessary so that it might exert itself to the point of its own ruin. And so no one has seen a tornado for a full day, not even for an hour. Their speed is extraordinary, and how short-lived they are, remarkable. The more forcefully and quickly it turns around the earth, the slacker it becomes, and, on account of this they fall apart. For it is made with the divided air troubled by some clouds, and it turns about, but making a ring around it, so that a part of the cloud is drawn in, as if it is inseparable from it, and it seizes it, moving in circles, its end is not to be found, turning in on itself again. From waves and from the sea it often sweeps up the waters under boats, and knocks sailors high from underneath: from land it scatters snatched up rocks and other animals and small trifles. Not only that by the lead rooves of temples and all sorts of houses, and indeed even those of the strongest materials, are seized by the air, and from elsewhere the air, joining more vigorously, carries it to an area further away. Most wisely, when huge stones have been rolled along from the windmill, sound against the storm, those people who are safe are taken to far off places. Indeed, so huge is the storm that descends that, enveloping the towns, citadels, and villages, rooves far and wide (so it is said) are bourn to the fields, according to Vincent, Book XXV, Speculum Historiae, Chapter LXXXVII, as he bears witness in Book XXVI, Chapter XXVI, making mention of the tornado. Not in the account of Diodorus Siculus, missing from Book VI of his Historia, saying the amazing force of the wind is in the directions of Aquilo. For in summer the Occidental and Septentrional last with such great force and vigour of the winds that it seizes rocks from the earth of such a size that a hand can hold. It builds them into piles that are not small as if they were sand or pebbles, and finally, from men it might snatch weapons and clothing, whereas from a horse it might steal their rider by force, as he mentioned in the next chapter. In fact, as it happens at some point in Vichia Norvegiae, through the air and the great burning sun, the largest fish in rich fishing places, driven from the streams, from their fishing poles like planks of wood in great heaps, were received as a gift given by God. But no one is entitled to demand action, for God reserves judgment to help he needy.
— "On the violence of the tornado, and the storm"

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.

Woodcut from the chapter "On the Signification of Thunderstorms for Every Specific Month"  from the History of the Nordic People by Olaus Magnus (source:

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).