References.—Enfield, “Hist. Phil.,” Vol. III. p. 430; “Le Cosmos” for May and June 1859, containing a very interesting series entitled, “Les Armées Météores”; Lardner, Vol. II. p. 113; Humboldt, “Cosmos,” 1859–1860, Vol. II. p. 335, and Vol. V. pp. 146–153; Julius Cæsar at A.D. 1590; Houzeau et Lancaster, Vol. II. p. 146; “Mém. de l’Acad. Royale des Sciences,” Vol. X. p. 737; “Phil. Hist. and Memoirs of the Royal Acad. of Sc.,” Vol. II. p. 281; “Geschichte der Mathematik,” Vol. IV. p. 474.
A.D. 1632.—Galileo (Galileo Galilei), Italian philosopher and mathematician, publishes his celebrated “Dialogo sopra i due massimi sistemi del mondo tolemaico e copernicano,” 4to, Fiorenza, from p. 88 of which is extracted the following passage:
Sagredus: “You remind me of a man who offered to sell me a secret for permitting one to speak, through the attraction of a certain magnet needle, to someone distant two or three thousand miles, and I said to him that I would be willing to purchase it, but that I would like to witness a trial of it, and that it would please me to test it, I being in one room and he being in another. He told me that, at such a short distance, the action could not be witnessed to advantage; so I sent him away and said that I could not just then go to Egypt or Muscovy to see his experiment, but if he would go there himself I would stay and attend to the rest in Venice.”
This Sagredus (Iohannes Franciscus), or Sagredo (Giovanni Francisco), besides being “a great magneticall man,” was a noble Venetian, even a doge, and had represented his country as ambassador at several courts. We read in Mr. Conrad W. Cooke’s very able article on William Gilbert of Colchester, originally printed in London “Engineering,” that this same Sagredus was the intimate friend of Galileo, and that, together with the powerful Sarpi, he used the whole might of his name and influence to protect the great philosopher and mathematician from the attacks of the clerical party. Pietro Sarpi, otherwise known as Father Paul, was, as already shown, a most illustrious Venetian scholar, who attained great proficiency in the medical and physiological sciences as well as in mathematics and in natural philosophy. Sagredus made several meritorious researches in magnetism, and, while on a voyage to Aleppo, ascertained the declination of the magnetic needle at that place. As a tribute to the scientific attainments of Sagredus, Galileo gave his name to one of the characters in his “Systema Cosmicum,” and many references to the work by William Gilbert are put into the mouth of Sagredus.
In further illustration of Galileo’s appreciation of Gilbert, the following is quoted from the great astronomer’s own writing: “I extremely admire and envy the author of ‘De Magnete.’ I think him worthy of the greatest praise for the many new and true observations which he has made, to the disgrace of so many vain and fabling authors, who write not from their own knowledge only, but repeat everything they hear from the foolish and vulgar, without attempting to satisfy themselves of the same by experience; perhaps that they may not diminish the size of their books” (Drinkwater’s “Life of Galileo”).
Galileo had also published, in 1630, the first edition of his “I discorsi e demonstrazioni ...” which Lagrange considers to be Galileo’s most substantial title to scientific glory.
References.—Galileo’s Biography in “Engl. Cycl.,” Vol. III. pp. 13–17; Miller, “Hist. Phil. Illust.,” London, 1849, Vol. III. p. 203, note; Nelli, “Vita,” 1793; Libri, “Hist. des Sc. Math.,” Paris, 1838, Vol. IV. pp. 157–294, 473–484; Houzeau et Lancaster, “Bibliog. Générale,” Vol. I. part i. pp. 655–657 for an analyzation of the works of Galileo, also Vol. II. pp. 137–145, 1576–1578; Wm. Whewell, “Phil. of the Ind. Sc.,” London, 1840, Vol. II. pp. 379–383; Guillaume Libri, “Histoire des Sc. Math.,” Halle, 1865, Vol. IV. pp. 157–302, and the notes; “Journal des Savants” for September and October 1840, for March and April 1841, for July to November 1858, for September 1868 and for October 1877; “Geschichte der Mathem.,” Vol. IV. pp. 4, 173, etc.; Larousse, “Dict.,” Vol. VIII. p. 954; “La Grande Encycl.,” Vol. XVIII. pp. 383–385; “Biog. Gén.,” Vol. XI. pp. 252–267; Fabroni (A.), “Vitæ Italorum,” 1778–1805, also “Elogi d’Illustri Italiani,” 1786–1789; likewise the very numerous entries concerning Galileo’s history, his Opponents, Supporters and School, which appear at pp. 331–357, Part I. of Libri’s “Catalogue,” published in 1861. Consult also “Galileo,” by Ed. S. Holden, in the “Popular Sc. Monthly” for January, February, May and June 1905; “Bibliot. Brit.,” Vol. XVI. N.S., 1821, pp. 3–21, 79–100, for an account of the life of Galileo by M. G. B. Clément de Nelli; “Journal des Sçavans,” Vol. LXX. for 1721, p. 350 in his “Saggiotore”; “Imperial Dictionary of Universal Biography,” published by Wm. McKenzie, London, pp. 536–539, giving an account of Galileo’s other discoveries.
A.D. 1635.—Delambre (J. B. J.) (1749–1822), professor of astronomy at the Royal College of France, refers (Vol. II. p. 545 of his “Histoire de l’Astronomie Ancienne,” 1817) to the mention made in “Procli Diadochi Paraphrasis Ptolem.,” lib. iv. “de siderum effectionibus,” 1635, p. 20, of the notion long current, especially along the shores of the Mediterranean, “that if a magnetic rod be rubbed with an onion, or brought into contact with the emanations of the plant, the directive force will be diminished, while a compass thus treated would mislead the steersman.”
References.—Humboldt, “Cosmos,” 1859, Vol. V. p. 156, also the entry at A.D. 1653. See likewise Whewell, “Hist. of the Ind. Sc.,” Vol. I. pp. 442, 443, 447, and the biography in the Supplement of the “English Cyclopædia,” pp. 539–541; “Journal des Savants,” for April 1828.
A.D. 1635.—Gellibrand (Henry), prominent English mathematician, professor of geometry and the successor of Edmund Gunter (A.D. 1624), in the chair of astronomy at Gresham College, publishes his discovery of the secular variation of the declination. The credit of this discovery has been by many given to John Mair. The diurnal and horary variation was found by Graham in 1722, and the annual variation was discovered by Cassini, 1782–1791.