It is said by Humboldt (“Cosmos,” 1849, Vol. II. p. 718, note) that this observation, the first of the kind, was made on the tower of the church of the Augustines at Mantua (Mantova) and that Grimaldi and Gassendi were acquainted with similar instances (instancing the cross of the church of St. Jean, at Aix, in Provence), in geographical latitudes where the inclination of the magnetic needle is very considerable. Some writers give Gassendi’s observation as occurring during 1632 (see Rohaulti, “Physica,” 1718, Par. III. cap. 8, p. 399; or, Rohault’s “System of Nat. Phil.,” 1728, p. 176).
“As the iron cross of an hundred weight upon the Church of St. John in Ariminum, or that load-stoned iron of Cæsar Moderatus, set down by Aldrovandus” (Sir Thomas Browne, “Pseudodoxia Epidemica,” 1658, p. 66).
Consult “Lettera dell’Eccel. Cavallara.,” Mantova, 1586, for a detailed account of this discovery, made January 6, of the last-named year. The iron rod supported a brick ornament in the form of an acorn, and stood on a pyramid at the summit of the belfry of the church of St. Augustine (Cabæus, “Philos. Magn.,” p. 62; “Ulysses Aldrovandi, Patr. Bonon ... Barthol. Ambros ...” Lib. i, cap. 6, p. 134).
For the account given by Aldrovandi of the Arimini observation and for references to Browne’s “Pseudodoxia Epidemica,” as well as to Boyle’s “Experiments,” see p. 53 of the valuable “Notes on the ‘De Magnete’ of Dr. William Gilbert,” by Silvanus P. Thompson, attached to the English translation of the original 1600 edition, which was so attractively produced by the Gilbert Club during the year 1900. Dr. Thompson further gives, at the page following (54), additional references to examples of iron acquiring strong permanent magnetism from the earth.
References.—Biography of Sarpi in the “Encycl. Brit.,” ninth edition, Vol. XXI. pp. 311–313; F. Micanzio, “Vita de F. P. Sarpi,” Verona, 1750; Rev. Alex. Robertson, “Fra Paolo Sarpi—the greatest of the Venetians,” 1894; Hallam, “Intro. to Lit.,” 1839, Vol. II. p. 464; U. Aldrovandi, “Musæum Metallicum,” 1648, p. 134; Tiraboschi, “Storia della Lettera,” Modena, 1794, Vol. VI. part ii. p. 506; Sarpi’s Complete Works, first published at Helmstat, 1750; Fabroni, “Vitæ Italorum,” Pisa, 1798; Giovini, “Vita,” Brussels, 1836; “Engl. Cycl.,” Biography, Vol. IV. pp. 695–697; Larousse, “Dict. Univ.” Vol. XIV. pp. 230–231; “History of the reign of Charles the Fifth,” by Wm. Robertson and Wm. H. Prescott, Philadelphia, 1883, Vol. III. p. 68; “Dict. Hist. de la Médecine,” N. F. J. Eloy, Mons, 1778, Vol. IV. pp. 180–181; “The Atlantic Monthly,” New York, January and February, 1904, wherein the author, Andrew D. White, ranks Sarpi with Machiavelli and Galileo; Libri, “Hist. des Sc. Mathém.” Paris, 1838, Vol. IV. p. 214, note.
A.D. 1632.—Gassendi (Pierre), an eminent French savant, professor at the Royal College of France, “ranked by Barrow among the most eminent mathematicians of the age, and mentioned with Galileo, Gilbert and Descartes,” discovers that a part of the iron cross of the Church of St. Jean at Aix possesses all the properties of a loadstone after being struck by lightning and lying in one position a certain length of time. Gilbert mentions, “De Magnete,” 1600, Book III. chap. xii.) that the fact of magnetism being imparted to an iron bar by the earth was first ascertained by examining the rod upon the tower of the church of St. Augustine at Arimini (Sir Thomas Browne, “Pseud. Epidemica,” London, 1650, p. 48; U. Aldrovandi, “Musæum Metallicum,” Milan, 1648, p. 134).
In the “Vie de Pierre Gassendi,” par le Père Bougerel de l’Oratoire, Paris, 1737, p. 14, it is related that during the month of September 1621, while promenading about three leagues’ distance from Aix in a village named Peynier, he observed a light in the heavens to which he gave the name of aurora borealis, as much on account of its location as by reason of its resemblance to the light which precedes the rising of the sun.
From the “History of the Royal Society,” by C. R. Weld, 1848, Vol. II. p. 430, is taken the following, communicated by Humboldt:
“The movement of the magnetic lines, the first recognition of which is usually ascribed to Gassendi, was not even yet conjectured by William Gilbert; but, at an early period, Acosta, ‘from the information of Portuguese navigators,’ assumed four lines of no declination upon the surface of the globe.... In the remarkable map of America appended to the Roman edition of the Geography of Ptolemy in 1508, we find, to the north of Gruentland (Greenland), a part of Asia represented and the magnetic pole marked as an insular mountain. Martin Cortez, in the ‘Breve Compendio de la Sphera’ (1545), and Livio Sanuto, in the ‘Geographia di Tolomeo’ (1588), place it more to the south. Sanuto entertained a prejudice, which, strange to say, has existed in later times, that a man who should be so fortunate as to reach the magnetic pole (Il calamitico) would then experience alcun miracoloso stupendo effecto” (“Cosmos,” translated under the superintendence of Col. Sabine, Vol. II. p. 280). In a footnote to the Otté translation of Humboldt, 1859, Vol. V. p. 58, it is stated that calamitico was the name given to the instruments in consequence of the first needles for the compass having been made in the shape of a frog.
In Gilbert’s “De Magnete,” allusion is made to Martinus Cortez, Book I. chap. i., also Book III. chap. i. and Book IV. chap. i.,[43] and to Livio Sanuto in Book I. chap. i., also in Book IV. chaps. i. and ix. In these several passages, Gilbert tells us that Martinus Cortez holds the loadstone’s seat of attraction to be beyond the poles, and he states the views of other writers in this respect, citing more particularly T. de Bessard (author of “Le Dialogue de la Longitude”), Jacobus Servertius (who wrote “De Orbis Catoptrici”), as well as Robert Norman, Franciscus Maurolycus, Marsilio Ficino, Cardan, Scaliger, Costa and Petrus Peregrinus (M. J. Klaproth, “Lettre à M. le Baron de Humboldt,” Paris, 1834, pp. 16–17, 37).