The year 1632 is justly remembered as the year Galilei's Dialogo sopra i due massimi sistemi saw the light. Yet the same year saw the publication of a huge number of works on Vesuvius, following the major eruption that began in the night between 15 and 16 December 1631. It was the most destructive eruption for more than a thousand years: the eruptive cloud reached approximately thirty miles in height and lava flows destroyed the towns at the foot of the mountain, an area that was thickly populated by poor people. To the surprise and relief of its inhabitants, Naples did not experience major destruction. An estimated four thousand people from the vicinity of Naples perished, and nearly forty thousand people from the countryside crowded into the city's churches. The eruption had a profound and lasting impact on Neapolitan political, religious and cultural life. Physicians, naturalists and churchmen observed, described and tried to explain what seemed to be an extraordinary event.

Cocco situates early modern literature on Vesuvius in its political and cultural context, paying special attention to the links between disasters and rebellion. As he puts it, ‘Channelling of popular expressions of piety into the formal cult of San Gennaro was a step toward preventing any potentially troubling interpretations of Vesuvius from gaining currency’ (p. 64). As in the past, the relics of San Gennaro played an important role in shaping the Neapolitans’ reaction to the disaster. The Jesuit Giulio Cesare Recupito pointed out in his De vesuviano incendio nuntius (1632) that the archbishop successfully organized the spiritual defence of the city by resorting to the relics of San Gennaro – whose links with Vesuvius had been established on the occasion of the AD 472 eruption. Braccini, an abbot from Lucca, author of one the most informative accounts of the 1631 eruption, referred to the Neapolitans’ fear turning to contrition and, finally, to the anxious hope that Naples would be spared the destruction. The 17 December procession, carrying the relics of the saint, displayed the civic unity of the city facing disaster.

Investigation of the causes of the eruption occupied a large portion of Braccini's Dell'incendio fattosi nel Vesuvio (1632), which resorted to the explosive power of saltpetre and vitriol contained in the bowels of the earth as a possible explanation of the phenomenon. Thanks to the Paracelsians, the search for chemical reactions occurring in the earth gained momentum, replacing the Aristotelian account as contained in Aristotle's Meteorologica. A major contribution to the chemical interpretation of geothermic phenomena came from Pietro Castelli, a physician and natural philosopher from Rome. Unlike Braccini, Castelli was no eyewitness to the eruption. He was asked to write on this topic by his patron, Cardinal Biscia, a task he promptly accomplished by publishing Incendio del Monte Vesuvio (1632). Castelli dealt with the 1631 eruption just tangentially, and gave an account of the different explanations of volcanism. He advocated the spagyrists’ analogy between the reactions obtained in the chemical laboratory and those occurring in nature. He included an appendix with a series of queries he had sent to a certain Frate Egidio, a member of the order of the Minim brothers, who watched Vesuvius and provided details about the eruption. According to Cocco, Castelli's questions ‘resembled Scholastic quaestiones in form … [and] may have derived from traditions of pedagogy and arguments suited for university debates’ (pp. 106–107). Although Cocco justly stresses that they were aimed at the empirical and particular, I am prone to read them as the outcome of Castelli's medical practice, rather than of a scholastic tradition.

Watching Vesuvius goes beyond the 1631 eruption by providing a cultural history of geology, mainly focused on Italian volcanoes and particularly Vesuvius. The second half of the book deals with scientists and savants who were engaged in observations and interpretations of volcanism in Campania and in Sicily, i.e. Giovanni Alfonso Borelli, Athanasius Kircher, Giuseppe Valletta, Giovanni Maria della Torre, Déodat Dolomieu and William Hamilton. One of its greatest strengths is that it gives prominence to the early modern iconography of Vesuvius. The positive impression of this stimulating and well-documented book is only slightly diminished by some mistakes, such as the statement on p. 93 that, ‘like Bruno and Campanella, he [Nicola Antonio Stelliola] later became an ardent supporter of Galileo’. Unfortunately, Giordano Bruno was burned at the stake in 1600, just too early to become Galileo's ardent supporter. The latter's Dialogo sopra i due massimi sistemi is referred to as Discorso su i due massimi sistemi (p. 81).