The Science of Magnetism Before Gilbert Leonardo Garzoni's Treatise on the Loadstone

Summary

This paper presents the main features of the treatise on magnetism written by the Jesuit Leonardo Garzoni (1543–92). The treatise was believed to be lost, but a copy of it has been recently recovered. The treatise is briefly described and analysed. The results of a comparison between Garzoni's treatise, Della Porta's Magia Naturalis (1589), and Gilbert's De Magnete (1600) are also summarized. As claimed in the seventeenth century by Niccolò Cabeo and Niccolò Zucchi, the treatise contains quite a lot of the material to be found subsequently in the Magia Naturalis and in the De Magnete. Most importantly, the treatise presents so many interesting features, well before Gilbert's work, which make it the first example of a modern treatment of magnetic phenomena.

Acknowledgments

It is a pleasure to thank Sabetai Unguru for his help in preparing the final version of this paper.

Notes

¹William Gilbert, De Magnete, magneticisque corporibus, et de magno magnete tellure; Physiologia nova, plurimis et argumentis et experimentis demonstrata (Londini, 1600).

²As a matter of fact, Robert Norman's The Newe Attractive, Shewing the Nature, Propertie, and Manifold Vertues of the Lodestone (Londini, 1581) could be connected with the De Magnete. On Norman's book, see note 37 below.

³Giovanni Battista Della Porta, Magiae Naturalis libri XX, ab ipso authore expurgati, et superaucti, in quibus scientiarum Naturalium divitiae, et delitiae demonstrantur (Neapolis, 1598). Book VII is entirely devoted to magnetism.

⁴The 1893 English translation by P. Fleury Mottelay reads: ‘Very recently Baptista Porta, a philosopher of no ordinary note, makes the 7th book of his Magia Naturalis a very storehouse and repertory of magnetic wonders; but he knows little about the movements of the loadstone, and never has seen much of them; much of what he has learned about its obvious properties, either from Messer Paolo, the Venetian, or through his own studies, is not very accurately noted and observed’.

⁵The 1658 English translation reads: ‘I knew at Venice, R.M. Paulus, the Venetian, that was busied in the same study. He was Provincial of the Order of Servants, but now a most worthy advocate, from whom I not only confess, that I gained something, but I glory in it, because of all the men I ever saw, I never knew any man more learned, or more ingenious, having obtained the whole body of learning; and is not only the splendor and ornament of Venice or Italy, but of the whole world’.

⁶See, for example, Timoteo Bertelli, ‘Sopra Pietro Peregrino di Maricourt e la sua epistola de magnete. Memoria Prima’, Bullettino di Bibliografia e di Storia delle scienze matematiche e fisiche I (1868), 1–98, and Id, ‘Sulla Epistola di Pietro Peregrino di Maricourt e sopra alcuni trovati e teorie magnetiche del secolo XIII. Memoria Seconda’, Ibid., 65–139 and 319–420.

⁷The sixteenth-century miscellaneous codex S 82 SUP is composed of many fascicoli, each written by several hands. See A. Rivolta, Catalogo dei codici pinelliani dell'Ambrosiana (Milan: tip. Pontificia Arcivescovile S. Giuseppe, 1933), 155, and P. Revelli, I codici ambrosiani di contenuto geografico, (Milan, tip. Pontificia Arcivescovile S. Giuseppe, 1929), 137. Though the codex had been described by Revelli, the presence of a copy of the lost treatise mentioned by Cabeo went unnoticed, until Ugo Baldini recovered it. See U. Baldini, Legem impone subactis. Studi su filosofia e scienza dei gesuiti in Italia 1540–1632 (Rome, 1992), 363–65.

⁸References to Garzoni's treatise come from the edition: L. Garzoni, Trattati della calamita, a cura di M. Ugaglia, Milan, FrancoAngeli 2005.

⁹ARSI, Rom. 78b, fols. 112^r, 212^r–v; Hist. Soc. 41, fol. 132^r; It. 84; Ven. 2, fols. 11^v; 14^r; 143^r; Ven. 117, fol. 143^v; Ven. 37, fols. 1^r; 3^r; 63^r; Ven. 105 II, fol. 337^r; Ital. 160, fol. 215^v; Ven. 3, fols. 191^v; 251^r; 317^v; 358^r; 396^v; 442^v; Bibl. Naz. Fondo Ges. 1645, fol. 105^v. See also Il Garzia, overo Nobiltà Heroica et Origine Regia della Nobilissima famiglia Garzia Hora detta Delli Garzoni Nobile Veneziana e bolognese, del Co: Giacomo Zabarella Cav. re Academico 1670 Apatista Gellato Incognito […], Archivio della Fondazione Querini Stampalia, Venezia (Ms. Classe IV Cod. 81), fol. 28^r.

¹⁰Antonio Possevino, Apparatus ad Philosophiam (Vicentiae, 1599), III.XIII, 107^r; III.XXXII, 163^r. See also Bibliotheca Selecta (Romae, 1593), XII, 103.

¹¹Niccolò Cabeo, Philosophia Magnetica in qua magnetis natura penitus explicatur (Ferrariae, 1629), Praefatio ad lectorem.

¹²See Niccolò Zucchi, Philosophia magnetica per principia propria proposita et ad prima in suo genere promota, Rome, Biblioteca Nazionale Vittorio Emanuele II, Fondo Gesuitico 1323, fols. 62^v–63^r.

¹³Every Jesuit province had to draw up and to send to Rome a catalogus annuus (or brevis) every year and a catalogus triennalis every three years.

¹⁴See U. Baldini (note 5), part IV.

¹⁵See Garzoni, Due trattati sopra la natura, e le qualità della calamita (henceforth referred to as Trattati), I.4, p. 105 (the pages are those of the edition referred to in note 8 above).

¹⁶The features of this section suggest that it was added at a later time, probably in view of the publication of the text, which Garzoni's death prevented. The publication of a text was subjected to severe restrictions. This means that also scientific works had to fit suitable philosophical prescriptions. In the case of the Trattati, in particular, the attempt of the author to arrange his results in a well-structured process of regressus is clear. Roughly speaking, Garzoni tries to supplement the induction of the cause from the experimental effect with a formal deductive descent from causes to experimental effects. In the debate of the time, in fact, this was the usual way to make a proof philosophically accettable.

¹⁷See also Trattati I.3, p. 97; II.II.13, pp. 304–5.

¹⁸Garzoni performed in Rome an experiment concerning the verticity acquired by an iron bar near the towers of the churches. We have only indirect evidence of the experiment. See Niccolò Cabeo, Philosophia Magnetica, IV.XI, 310; Niccolò Zucchi, Philosophia magnetica … fols. 62^v–63^r.

¹⁹Petrus Peregrinus de Maricourt, Opera, eds. L. Sturlese and R. B. Thomson (Pisa, 1995).

²⁰See, in particular, Albertus de Saxonia, Questiones subtilissime in libros Aristotelis de celo et mundo, (Venetiis 1492, reprint Hildesheim 1986), and Themo Judaeus, Quaestiones perspicacissimi philosophi Thimonis super quatuor libros meteororum, in Caietanus de Thienis, Libri Metheororum Aristotelis Stagirite peripatheticorum principis cum commentariis … (Venetiis, 1522).

²¹Aristoteles, De Anima 405a19–20; Physica 266b27–267a12. Johannes Philoponus, Commentaria in Analytica Posteriora, I.1, 12, 24–28 (Wallies); Commentaria in de Anima, I.2, 86, 16–26 and I.3, 120,19–32 (Hayduck); Commentaria in Physica, III.4 403,18–32 (Vitelli); De Aeternitate Mundi contra Proclum, H. Rabe, ed. (Leipzig, 1899) 245, 22–29; 274,1–275,17. Themistius, In libros Aristotelis de anima paraphrasis, I.2, 13,21–23 (Heinze); Analyticorum posteriorum paraphrasis, I.1 2,28–30 and II.15, 59,35–60,4 (Wallies); In Aristotelis physica paraphrasis, VIII.10 234,7–235,17 (Shenkl). Plinius, Naturalis historiae libri XXXVII, ed. L. Jan, C. Mayhoff (Leipzig, 1892–1909, reprint Stuttgart, 1967–1996) XX 2; XXXIV 147; XXXVI 127–130; XXXVII 61. Augustinus Aurelius (St.), De Civitate Dei libri XXII, ed. B. Dombart, A. Kalb (Leipzig und Stuttgard, 1978–1981; reprint 1993), XXI.4.

²²Alexander Aphrodisiensis, Quaestiones, II.23, 72,9–74,30 (Bruns). Lucretius, De rerum natura, VI (906–1089). Plato, Io 533b–e; 535e–536b; Timaeus 80b–c. Plutarchus, Quaestiones Convivales, in Moralia, ed. W. Nachstädt, W. Sieveking, J. Titchener, vol. IV (Leipzig, 1935, reprint Leipzig und Stuttgart, 1971). Claudius Galenus, De naturalibus facultatibus I.14, Opera Omnia, editionem curavit C. G. Kühn, 20 vols. (Lipsiae, 1821–33, vol. 2), and De Theriaca ad Pisonem III (Kühn, vol. 14-1). See also De locis affectis, VI.5 (Kühn, vol. 8); De simplicium medicamentorum temperamentis ac facultatibus, III.25 and IX.2 (Kühn, vols. 11–12), De succedaneis (Kuhn, vol. 19). Averroës, Aristotelis stagiritae de physico auditu libri octo, VII, Summa 3 and VIII, Summa 2, in Aristotelis Opera cum Averrois commentariis (Venetiis 1562–74, reprint Frankfurt am Main, 1962, vol. IV). Albertus Magnus, De Mineralibus II.II.I and II.II.XI; De Natura loci I.V; De Apprehensione I.XI, in Opera Omnia, Cura ac labore A. et Aem. Borgnet (Parisiis, 1890–99, vol. V). St. Thomas Aquinas, In octo libros Physicorum Aristotelis expositio, ed. M. Maggiolo (Taurini-Romae, 1954) VII.II, lect. III [903].

²³Vincentius Burgundius Bellovacensis, Speculum naturale, VIII.XX; VIII.XXXIX–XL, in Speculum quadruplex, sive speculum maius, naturale, doctrinale, morale, historiale (Venetiis, 1591); Marsilius Ficinus, De vita caelitus comparanda, III.XV, in Three Books on the Life, A critical edition and translation with introduction and notes by C. V. Kaske and J. R. Clark (Binghamton, 1989); Gerolamo Fracastoro, De sympathia et antipathia rerum liber unum item de contagione et conagiosi morbis, et eorum curatione libri III (Lugduni, 1554), VII; Gerolamo Cardano, De Secretis, V and XVII; De Subtilitate, V and VII; De rerum varietate, IX.XLVIII; XI.LIV, in Opera Omnia, cura C. Sponii (Lugduni, 1663).

²⁴Francesco Maurolico, De lineis horariis, X, in Opuscola Mathematica (Venetiis, 1575). See also Problemata Mechanica cum appendice, et ad Magnetem, et ad Pixidem Nauticam pertinentia (Messanae, 1613).

²⁵Camillo Leonardi, Speculum Lapidum (Venetiis, 1502), II. Martin Cortés, Breve compendio de la sphera y de la arte de navegar (Sevilla, 1551), III. Ignazio Danti, Dell'uso et fabrica dell'astrolabio (Firenze, 1578), II.VI.

²⁶ Die pilosophischen Werke des Robert Grosseteste, Bischofs von Lincoln, ed. L. Baur, Münster, 1912; John Peckham, Perspectiva communis libri tres, in D. C. Lindberg, editor, John Pecham and the Science of Optics: Perspectiva communis (Madison, WI, 1970); Henry of Langenstein, Quaestiones super perspectivam, in Praeclarissimum mathematicarum opus in quo continetur perspicacissimi mathematici Thome Bradwardini Arismetica et eiusdem Geometria, necnon et sapientissimi Pisani Carturiensis Perspectiva […] cum acutissimis Joannis de Assia super eadem perspectiva questionibus annexis … (Valentia, 1503); Themo Judaeus, Quaestiones super quatuor libros meteororum (note 18).

²⁷See Trattati I.9, pp. 167–79.

²⁸The term intentional comes from intention (latin intentio, arabic ma'na), which in the neo-Platonic Arabic tradition means the relationship between an act and its object; it spread in the Latin West after the translation of the Metaphysics of Avicenna (see I.II). About the use of the term in logic, see for example J. Pinborg, Logik und Semantik im Mittelalter (Stoccarda-Bad Cannstatt, 1972), section. 4.2.1 in particular, and A. Maierù, Terminologia logica della tarda scolastica (Rome, 1972).

²⁹See, for instance, S. Thomae Aquinatis, In Petri Lombardi IV libros sententiarum, II, dist. 13, q. 1, a. 3 c.

³⁰ Trattati I.9, p. 179.

³¹‘Non ci rende intorno al sapere la causa di questo effetto molto più dotti, che prima’ (p. 218).

³²See Trattati I.15, pp. 238–41.

³³Garzoni obtains the same graphical representation of the verticity's diffusion moving a compass near the loadstone (Trattati II.I.60–60.1, p. 275).

³⁴On the contrary, as Garzoni correctly observes in Trattati I.15, p. 238, loadstones of comparable size are needed to observe the mutual magnetic action.

³⁵Garzoni's approach to intentional species, and in particular his way of revealing the virtual alteration of the medium by means of what is nowadays termed a ‘test particle’, provides new and interesting elements for a clarification of the origins of the notion of field. The subject will be discussed in detail in a subsequent work.

³⁶See Magia Naturalis, lib. VII, capp. XV and XXVI; De Magnete, II.VI; II.VII; II.XXVII; V.XI.

³⁷See, in particular, the diagrams accompanying chapter II.VI and V.XI.

³⁸ The Newe Attractive is composed of two parts: a general exposition of the magnetic phenomena and a more detailed investigation of the problem of the magnetic dip. The second part has no correspondence with the Trattati, where the existence of the phenomenon is firmly denied, but the material presented in the first part is a subset of the material of the Trattati. Norman describes the following effects. The loadstone can transfer its virtue to a needle, the needle to another, and so on (chap. I, p. 7, cfr Trattati II.I.8). The loadstone can magnetize an infinite number of needles, but its virtue is thereby not weakened (chap. I, pp. 7–8 and p. 9, cfr Trattati II.I.9). Two magnetized pieces of iron passed through a light piece of wood and floating in water attract each other by means of the dissimilar faces and repel by means of the similar faces (chap. I, pp. 8–9, cfr Trattati II.I.23). The free loadstone oscillates and then places itself with the north face towards the attractive point (chap. I, p. 9, cfr Trattati II.I.1). The face of a piece of iron touched by the north face of the loadstone faces to South, and vice versa (chap. I, pp. 9–10, cfr Trattati II.I.13.5). Such a large number of coincidences can be ascribed, at least in part, to a common source, i.e. Peregrinus’ Epistula. Moreover, Norman does not construct a true theory of magnetism, but just touches on some issues, supported by just a few experiments; a comparison of the two works is therefore hardly fruitful.

³⁹R. Norman, The Newe Attractive (note 2) ch. I.

⁴⁰R. Norman, The Newe Attractive (note 2) ch. V.

⁴¹R. Norman, The Newe Attractive (note 2) ch. VIII. See, in particular, pp. 30–31.

⁴²And surely I am of opinion, that if this Vertue could by any meanes be made visible to the Eye of man, it would be found in a Sphericall forme, extending rounde about the Stone in great Compasse, and the dead bodie of the Stone in the middle thereof: Whose center is the center of his aforesaid Vertue. And this I have partly prooved, and made Visible to be seene in some manner, and God sparing mee life, I will heerein make further Experience, and that not curiously, but in the Feare of God, as neere as he shall give mee grace, and meane to annexe the same unto a Booke of Navigation, which I have had long in hand. (ch. VIII, p. 31).

⁴³See, for instance, Trattati I.11, pp. 191–92.

⁴⁴ Trattati I.7, pp. 130–31. See also II.I.71–73, pp. 280–81.

⁴⁵The number of pages of Della Porta's book is referred to the edition Francofurti 1591.

⁴⁶The 1658 English translation reads:

I pounded a Loadstone into powder, some very small, some something gross. And I made some of little bits, that they might better represent troops or horse, or companies of foot. […] Under a smooth table I put a very principal Loadstone with my hand. When this was put there, the left wing marched, and on the right hand, with another stone, the right wing marched. When they drew near together, and were more near the Loadstone, the sands trembled. And by degrees, they seemed like those that take up their spears. […] But this is the greater wonder, because what is done on a plain board, may be done hanging in the air. That you may see them like the Antipodes in battle. For stretching out a paper, or setting a table aloft, the Loadstone moved above the table, will do the same thing we speak of, and show it to the spectators.

⁴⁷The English translation of this and the following quotations from Garzoni's Trattati are by S. Unguru:

For this purpose, if one places under a sheet of paper, on which filings of iron were spread, a powerful piece of the stone, the filings come together, as if they were bristles, or standing-up hairs, that rise up in a certain way and, when the stone is moved by hand, these hairs run and move as soldiers, scouring alive all over the paper.

⁴⁸And if one interposes here another sheet of paper, placing the stone over it, in such a manner that it touches it, and then one superimposes the sheet so that it touches the pilings of iron, the stone will hold suspended many of those [metallic] hairs, which, whenever the stone moves, will also go, like certain antipodes, moving with their feet upwards and scouring in a certain way; and when the loadstone is lifted from above the sheet, the pilings which were suspended underneath shall suddenly fall downwards, not having anymore the virtue of the loadstone which sustained and suspended them.

⁴⁹The 1658 English translation reads:But if we rub an Iron ring on the one side with a Loadstone, then the part that is touched, will receive the Virtue of the part of the Loadstone that touched it. And the opposite part will receive the contrary. And therefore the middle of the Iron ring will be capable but of half the force of it, as if it were straight. But if we make a pin round as a ring. And the part jointed together with a joint, be rubbed with a Loadstone. And being rubbed, be stretched straight again, the ends shall receive the same Virtue, be it northern or southern. But by degrees that force will grow feeble. And in a short item become northerly, and the other southerly, or will receive more Virtue then it first had. May be when it was touched farther from the end.

⁵⁰In a ring of iron, the virtue spreads itself half here half there, beginning at the spot where contact is made; at that point, the virtue of one face imprints itself and, at the opposite point, the virtue of the other.

From which it is clear that an iron twisted in the shape of a ring, is capacious of only half the virtue of which it would be capacious, had it been straightened.If an iron wire is forced into ring-shape, and at the point opposed to the juncture, it is applied to the loadstone, in such a manner that it remains suspended there, then, if after it has gained the virtue, it will be forced open and straightened, suddenly the two ends will have the very same virtue, either both septentrional or both meridional, but then, gradually, one of the said extremities shall turn towards the contrary virtue, thus losing in great part its first [original] virtue.

⁵¹Cfr. Trattati I.10, pp. 184–85; II.I.60, p. 275, where Garzoni states that the magnetical quality spreads off from loadstone's extremal points as from two centres, and Trattati I.9, p. 164, where he says that the quality gradually diminuishes, going from the centre.

⁵²In order to explain the transmission of the loadstone's virtue, for example, he resorts to the hairs produced near the poles by confrication (Magia Naturalis, VII.XII).

⁵³See De Magnete III.XIV.

⁵⁴Let us notice in particular the similarity between Garzoni's sentence operare solo con differenza di sito and Della Porta's situm tam dissimilia operari.

⁵⁵The 1658 English translation reads:

Wherefore in the Mariners Compass, or in other uses, when the Iron is stupefied by the touch of other things. And has not its due forces to free it from this imperfection, we put it into the fire. Hence, we find the error of many men, who when they put the Needle into the Compass, they first make it red hot. And then they rub it with the Loadstone, supposing it will by that means, take in the Loadstones virtue the more. But they do not only by contraries, but they so make void the Loadstones Virtues, that it cannot do its office.

⁵⁶The 1658 English translation reads: ‘but that force is driven out of the Iron by the fire. And it is just as it was before it was touched with the Loadstone. Wherefore, as often as that force is driven away with the fire, we may touch it again, and give it the same force’. Notice that the phrase ‘faciei virtus’ has disappeared from the translation.

⁵⁷‘When the virtue of the two faces (sides) of the iron is annihilated, there always remains that of only one face’. ‘The virtue of the two faces of the iron [is such] that no matter how many times it is annihilated by fire, it can be returned an equal number of times by the loadstone’.

⁵⁸‘Actually, the more the iron is refined by fire, [thus] freeing itself of rust, the more the said virtue of one face is also refined and awakened’.

⁵⁹Like many of his contemporaries, Gilbert perhaps underestimated the fact that Garzoni's results were reminiscent of this context. And that it was not enough to propose alternative interpretations of the terms to make them objective and arbitrarily replaceable. Futhermore, Gilbert presumably did not have direct access to Garzoni's treatise, but to a partly modified version (see the next section).

⁶⁰The number of pages of De Magnete refers to the edition Londini 1600.

⁶¹To explain the variations of inclination, Gilbert resorts to the different intensity of the magnetic attraction. Then, he connects the intensity with the length of the chord the prolongation of every piece of iron leaves on the terrella (De Magnete, II.XIV, pp. 81–82). As Cabeo already noticed (Philosophia Magnetica, II.X, pp. 140–41) this is a vicious circle. The alternative explanation Cabeo offered in the following chapter is taken from Garzoni (Trattati, II.II.15, pp. 310–13).

⁶²See, for instance, the experiment with the iron ring discussed in the previous section and expounded in a very similar way also in De Magnete, III.V, pp. 129–30.

⁶³For instance, both Garzoni and Gilbert discuss the power of the loadstone to transmit its virtue to an infinite number of needles without diminishing its force (De Magnete, I.XVI, p. 38, cfr. Trattati, II.I.9, p. 262), and both the authors say that magnetized iron acts more than the loadstone (De Magnete, II.IV; II.XXVI, cfr. Trattati, II.I.33, p. 269). But the first result is quoted also by Norman (The Newe Attractive, ch. I) and the second one by Cardano (De Subtilitate, book VII).

⁶⁴Jean de Sancto Amando, Expositio super Antidotarium Nicolai, in Giovanni Mesua, Opera (Venetiis 1581), fol. 232. About St-Amand's work, see for instance L. Thorndike, John of St. Amand on the Magnet, Isis 36 (1945), 156. About a possible common source of St-Amand and Peregrinus, see W. Wenckebach, Sur Petrus Adsigerius et les plus anciennes observations de la déclinaison de l'aiguille aimantée, Annali di Matematica Pura ed Applicata, 3 (1865), 159–68.

⁶⁵Francesco Griselini, Memorie anedote spettanti alla vita ed agli studj del sommo Filosofo e Giureconsulto F. Paolo Servita (Losana, 1760), 32–33 and 38–39.

⁶⁶ Miscellanea di storia veneziana, Venice, Biblioteca Nazionale Marciana, mss. Italiani cl. 11, n° 123 (6932), fols. 221^v; 362^v; Opuscoli e frammenti del Padre Paolo Sarpi, Venice, Biblioteca Nazionale Marciana, mss. Italiani, cl. 2, n° 129 (4914), p. 170; p. 279.

⁶⁷About Pinelli's studio, see for example A. Favaro, Galileo Galilei e lo studio di Padova, 2 vols (Padua, 1966), I, 52–59; Paolo Gualdo, Vita Ioannis Vincentii Pinelli, Patricii Genuensi. In qua studiosis bonarum artium, proponitur typus viri probi et eruditi (Augustae Vindelicorum, 1607). About the relation between Sarpi and Pinelli, see G. Cozzi, Paolo Sarpi tra Venezia e l'Europa (Torino, 1979) and L. Sosio, ‘I “Pensieri” di Paolo Sarpi sul moto’, Studi Veneziani, XIII (1971), 315–67 (354).

⁶⁸Fulgenzio Micanzio, Vita del padre Paolo dell'ordine de’ servi e teologo della Serenissima Repubblica di Venezia (Leida, 1646); Francesco Griselini, Memorie anedote (note 54); Id., Il genio di F. Paolo Sarpi in ogni facoltà scientifica e nelle dottrine ortodosse. Tendenti alla difesa dell'originario diritto de’ sovrani ne’ loro rispettivi dominj, ad intento che colle leggi dell'ordine vi rifiorisca la pubblica prosperità (Venezia, 1785). For a critical answer to this, see Appiano Buonafede, Della impudenza letteraria. Sermone parenetico di Agatopisto Cromaziano contro un libro intitolato Memorie Anedote spettanti alla vita agli studij di F. Paolo Servita, raccolte e ordinate da Francesco Griselini (Lucca, 1761).

⁶⁹See for instance I Pensieri di P. Sarpi, eds. L. Cozzi and L. Sosio (Torino, 1996).

⁷⁰See I Pensieri di P. Sarpi (note 58), 147 (pensieri n° 128 and 129); 170 (n° 184); 173 (n° 186); 210 (n° 239); 236 (n° 278), and 362 (n° 488).

⁷¹See I Pensieri di P. Sarpi (note 58), 147 (pensieri n° 128 and 129); 170 (n° 184); 173 (n° 186); 210 (n° 239); 236 (n° 278), and 362 147 (n° 128 and 129).

⁷²See Boris Ulianich, Paolo Sarpi. Lettere ai gallicani (Wiesbaden, 1961), and in particular the letters to Jacques Leschassier (4 September 1607, p. 4; 11 December 1607, p. 6; 1607, p. 7; 18 March 1608, p. 10; 13 May 1608, pp. 13–14; 3 February 1610, pp. 67–68). Another interesting letter concerning the magnetism was written to Galileo on 11 September 1602. See Galileo Galilei, Opere, 20 vols (ed. Nazionale a cura di A. Favaro, Firenze, 1890–1909), X, 91–93.

⁷⁶The passage is quoted from Sarpi's letter to Alvise Lollino, bishop of Belluno. See B. Ulianich (note 61) p. 256.

⁷³The documents are: a brief summary of the work, contained in F. Griselini, Memorie anedote (note 54) 32–33 and 35–42; a second brief mention contained in Marco Foscarini's notes to his history of the Venetian literature (Venice, Biblioteca Nazionale Marciana, mss. Italiani, cl. 11, n° 123 (6932), fol. 362^v; mss. Italiani, cl. 2, n° 129 (4914), p. 170; the same observations are summarized at p. 279); some anonymous notes (of the middle of XVIII century) referring the results of a comparison between Sarpi's treatise and Musschenbroek's works on magnetism; two observations due to Bonfiglio Capra and contained in Foscarini's notes.

⁷⁴See F. Griselini, Memorie anedote (note 54) 32–33.

⁷⁵‘That Englishman Gilbert seems not to write eruditely [i.e. in a florid style] but [merely] soundly. All those who have dealt with some aspects of the loadstone [before him] have merely stammered; this one is the first who really writes’.