At pp. 7 and 8 of his “Terrestrial and Cosmical Magnetism,” Cambridge, 1866, Mr. Walker gives extracts from the twelve chapters of Burrowes’ work which, “containing, as it does, the first recorded attempt at deducing the declination of the needle from accurate observations, must be considered as making an epoch in the history of terrestrial magnetism.”
References.—Johnson, “New Univ. Encycl.,” 1878, Vol. III. p. 230, and the tables of the variations at pp. 274–275 of Vol. II. of Cavallo’s “Elements of Natural Philosophy,” 1825. See the photo reproduction of “A Discourse ...” 1596 ed. in G. Hellmann’s “Neudrucke ...” 1898, No. 10.
A.D. 1585.—Juan Jayme and Francisco Galli made a voyage from the Philippines to Acapulco, solely for the purpose of testing by a long trial in the South Sea a declinatorium of Jayme’s invention, from which M. de Humboldt says (“Cosmos,” 1859, Vol. V. p. 56) some idea may be formed of the interest excited in reference to terrestrial magnetism during the sixteenth century.
A.D. 1586.—Vigenere (Blaise de), in his annotations to Livy (“Les cinq premiers livres de Tite-Live,” Paris, 8vo, Vol. I. col. 1316) alludes to the possibility of communicating the contents of a letter through a thick stone wall by passing a loadstone over corresponding letters circumscribing the compass needle.
References.—“Emporium of Arts and Sciences,” Vol. I. p. 302; Fahie, p. 20.
A.D. 1589.—Acosta (Joseph d’), learned Jesuit, who has been already mentioned under the A.D. 121 entry, says in Chap. XVII. lib. i. of his masterly “Historia Natural de las Indias” (“Histoire Naturelle et Moralle des Indes tant Orientalles qu’Occidentalles,” traduite par Robert Reynault Cauxois, 1598, 1606) that he is able to indicate four lines of no variation (instead of one only discovered by Columbus) dividing the entire surface of the earth: “foure poyntes in all the world, whereas the needle looked directly towards the North.” Humboldt remarks that this may have had some influence on the theory advanced, in 1683, by Halley, of four magnetic poles or points of convergence.
References.—Humboldt, “Cosmos,” 1859–1860, Vol. I. pp. 66, 193, note; Vol. II. pp. 280, 281; Vol. V. p. 140.
A.D. 1590.—Cæsare (Giulio-Moderati), a surgeon of Rimini, observes the conversion of iron into a magnet by position alone. This effect was noticed on a bar which had been used as a support to a piece of brickwork erected on the top of one of the towers of the church of St. Augustine as is mentioned at the 1632 entry of Pietro Sarpi.
A.D. 1597.—Barlowe—Barlow (William)—who died May 25, 1625, and was Archdeacon of Salisbury—publishes his “Navigators’ Supply,” from which the following is extracted: “Some fewe yeares since, it so fell out that I had severall conferences with two East Indians which were brought into England by Master Candish (Thomas Cavendish, one of the great navigators of the Elizabethan Age) and had learned our language.... They shewed that in steade of our compas they (in the East Indies) use a magneticall needle of sixe ynches long ... upon a pinne in a dish of white china earth filled with water; in the bottome whereof they have two crosse lines for the foure principall windes, the rest of the divisions being reserved to the skill of their pilots.”
Barlowe also published in 1613, 1616 and 1618 different editions of his work on the magnet, the full title of the last named being “Magneticall Advertisements or diuers pertinent obseruations and approued Experiments concerning the nature and properties of the Loadstone. Whereunto is annexed a briefe Discoverie of the idle Animadversions of Mark Ridley, Dr. in Physike upon this treatize.”[28] Therein (Preface to the reader), he speaks of “That wonderful propertie of the body of the whole earth called the magneticall vertue (most admirably founde out and as learnedly demonstrated by Doctor Gilbert, physitian vnto our late renowned soveraigne Queen Elizabeth of happy memory) is the very true fountaine of all magneticall knowledge. So that although certain properties of the loadstone were knowne before, yet all the reasons of those properties were vtterly vnknowne and never before revealed (as I take it) vnto the sonnes of man....” Just before the Preface appears the following letter which (as William Sturgeon remarks) affords a good idea of the opinion entertained by Gilbert of Barlowe’s talents in this branch of science: “To the Worshipfull, my good friend, Mr. William Barlow, at Easton by Winchester. Recommendations with many thanks for all your paines and courtesies, for your diligence and enquiring, and finding diuers good secrets, I pray proceede with double capping your Loadstone you speake of, I shall bee glad to see you, as you write, as any man. I will haue any leisure, if it were a moneth, to conferre with you, you haue shewed mee more,—and brought more light than any man hath done. Sir, I will commend you to my L. of Effingham, there is heere a wise learned man, a Secretary of Venice, he came sent by that State, and was honourably receiued by her Majesty, he brought me a lattin letter from a Gentleman of Venice that is very well learned, whose name is Iohannes Franciscus Sagredus, he is a great Magneticall man and writeth that hee hath conferred with diuers learned men of Venice, and with the Readers of Padua, and reporteth wonderfull liking of my booke, you shall haue a coppy of the latter: Sir, I purpose to adioyne an appendix of six or eight sheets of paper to my booke after a while, I am in hand with it of some new inuentions, and I would haue some of your experiments, in your name and inuention put into it, if you please, that you may be knowen for an augmenter of the art. So far this time in haste I take my leaue the XIII of February. Your very louing friend, W. Gilbert.”