Trattati della Calamita (review)

With this edition of a sixteenth-century treatise on magnetism, previously known only from contemporary references, Monica Ugaglia fills a long-noted lacuna in the history of science, and presents historians with the raw materials for a better understanding of early modern views of occult qualities, experiment, and natural philosophy.

Ugaglia presents a critical edition of the only known copy (unfortunately incomplete) of the Due trattati . . . della calamita, the "Two treatises . . . on the lodestone" written by a Venetian Jesuit, Leonardo Garzoni (1543-92). The volume includes an eighty-page introduction, a transcription of the treatises themselves, and a concordance table comparing the Trattati with three contemporary considerations of magnetism: Niccolò Cabeo's Philosophia Magnetica, Giambattista della Porta's Magia Naturalis, and William Gilbert's De Magnete.

Garzoni's first treatise explains his theory of magnetism and the loadstone, while the second describes ninety empirical findings on magnetism followed by an analysis of each that breaks off after examining only eighteen. True to his Jesuit training, Garzoni sought to provide a thoroughly Aristotelian theory of magnetism in opposition to the animistic accounts of Neoplatonists and others, including Gilbert. At the core of Garzoni's theory were two primary, nonoccult qualities — one inherent in the form of loadstones and the other in that of (unmagnetized) iron — which, he argued, are responsible for all magnetic phenomena.

Ugaglia contends that the recovery of Garzoni's theory and empirical findings requires a reevaluation of early modern science in general, and the history of magnetism in particular. Historians have long recognized that Garzoni's contemporaries owed him intellectual debts, but without his treatise, the precise nature of these connections remained unclear. Manuscript in hand, Ugaglia fills in the details: she deems della Porta a plagiarist who mangled the Jesuit's findings, but judges Cabeo an honest follower who advanced toward what she implies was the ultimate goal — Gilbert's idea of the earth itself as a lodestone. Ugaglia also clears Gilbert of plagiarism, but emphasizes his reliance on Garzoni's empirical findings. Finally, Ugaglia argues that Gilbert and della Porta both learned their Garzoni through a (now-lost) treatise by the famous Venetian gadfly Paolo Sarpi, who transmitted the Jesuit's ideas in a condensed form. This conclusion remains conjectural unless and until Sarpi's text turns up.

In addition to reordering the intellectual history of magnetism, Ugaglia wishes to highlight Garzoni's methodology, which she deems at least as experimentally-based as Gilbert's. She further suggests that Garzoni's experimental approach to natural philosophical problems was typical of Jesuit scientists. Ugaglia's efforts here are useful, but incomplete. Ugaglia is less sensitive than one might wish to the variety of practices covered by the term experiment, and too casually sets aside Garzoni's use of "common experience" as irrelevant to her analysis (36-37). She comments on Garzoni's distrust of magnetic variation data gathered by sailors and navigators, but does not draw more general connections to early modern attitudes towards craft knowledge or discussions of the value and limitations of experimental and experiential knowledge. In the end, Ugaglia is interested in comparing Garzoni's methodology to Gilbert's, but not to that embraced by, say, Paracelsus, Bacon, or Gassendi.

On the whole, Ugaglia's edition is well-executed. One particularly commendable aspect is the faithful reproduction of the manuscript's many drawings, which are uniformly clear if sometimes rather small. One minor annoyance: as there is only a partial table of contents for the treatises themselves and no running headers with section numbers, the many cross-references given by section rather than page number can be tedious to find.

With this volume, Monica Ugaglia provides a fine tool for further work on early modern magnetism and, more broadly, natural philosophy. She rightly notes that our knowledge of magnetism before Gilbert is remarkably thin, which makes this volume an important contribution to the existing literature. Ugaglia convincingly shows that the accepted ebb and flow...