Chapter 4 Heat and Moving Spirits in Telesio’s and Della Porta’s Meteorological Treatises

Arianna Borrelli

1 Introduction

In the year 1610, at the festivity of St. Peter and Paul, forbidden books were burned in front of the cathedral of Naples. According to an extant list, among them were “several volumes of Bernardino Telesio’s De rerum natura [On the Nature of Things]” and “the works of Telesio”.1 In the same year, the meteo- rological treatise De aeris transmutationibus (On the Transmutations of Air) by the Neapolitan scholar and experimenter Giambattista Della Porta was published in Rome with the imprimatur of the Court of the Holy Office of the Inquisition.2 Given these premises, it would be very surprising to find Telesio’s name mentioned in Della Porta’s treatise, and indeed that was not the case. Moreover, given Della Porta’s experimental interests and syncretic style and Telesio’s more systematic approach to natural philosophy, it might appear that their writings would hardly display points of similarity. Yet I will argue that, at least as far as meteorology is concerned, their works have more in common than one might expect. In his short booklet De iis quae in aere fiunt et de terraemotibus (On What Takes Place in the Air and on Earthquakes, 1570) Telesio used meteorology to offer an example of how his natural philosophy fared in practice, but the text was also part of a broader contemporary trend.3 In the Renaissance there was a growing interest in describing, explaining, and predicting meteorologi- cal phenomena. This was spurred by factors ranging from reports of exotic weather from the East and West Indies to the revival of Stoic philosophy and the increasing social and economic significance of winds and water flows. The explanation of weather phenomena also had a political significance be- cause extraordinary “meteorological” events, which at the time also included

1 “Berardini [sic] Telesii de rerum natura, più volumi”, “Telesij opera”, see Agrimi, “Telesio nel Seicento napoletano,” 345. 2 Paolella, “Prefazione,” xiv. 3 Telesio, De iis quae in aere fiunt et de terraemoribus (1570).

© Koninklijke Brill NV, Leiden, 2019 | doi:10.1163/9789004352643_006 Heat and Moving Spirits in Telesio’s and Della Porta’s 67 earthquakes and comets, could be seen as announcements/messengers of divine punishment for lay and religious leaders. Telesian meteorology builds upon the Aristotelian framework regarding “vapors” emitted by earth and water under the influence of the Sun as the material out of which all weather events are made. However, Telesio holds very different views from Aristotle on how the Sun acts upon bodies and disagrees with the Stagirite because he conceives that vapors are capable of moving of their own will, prompted by a desire to escape condensation or rarefaction. Telesio’s meteorological explana- tions are based on his own general view of natural phenomena, but they also reflect notions that were starting to shape meteorology in his age and which were central to Della Porta’s On the Transformations of Air. Della Porta’s treatise is longer and of broader scope than Telesio’s booklet and combines detailed discussions of how the various meteorological phenomena are to be explained, with descriptions of their role in everyday life and of the various traditions and superstitions associated with them.4 In his treatise Della Porta is not primarily interested in explaining weather and climate according to some predetermined natural philosophical frame- work, and he is happy to combine ideas from different world views. He deploys a bottom-up approach to investigating nature, regarding each phenomenon in its empirical details and trying as far as possible to illustrate the origin of wind, rain, or thunder by means of simple experiments, which he usually states he has performed personally in front of an audience. However, Della Porta also presents his meteorology as embedded in an overarching natural philosophi- cal context, albeit a rather sketchy one, and assumes that all meteorological phenomena result from the transmutations of the element “air”. For Della Porta there are no vapors coming from the earth or the sea, and this point sets him in contrast to both Aristotle and Telesio. Yet he regards the heating action of the Sun as the main motor of weather and climate, as Telesio does, and also shares Telesio’s notion that the matter out of which winds, rains, and other phenomena are made is not passive but displays a degree of indepen- dent activity. Although these general similarities between the two authors can easily be attributed to more general trends of thought in their time, there are also more specific parallels between their meteorological works, and I believe that locating and analyzing them will contribute to a better understanding and contextualization of the development of natural philosophy in southern Italy around 1600. This paper aims to elaborate such a comparison between the two authors. Following a short overview of the many facets of Renaissance meteorology (section 2), I will discuss the contents of Telesio’s meteorological

4 Della Porta, De aeris transmutationibus [1610] (2000).