=A.D. 1581.=--Burrowes--Borough--Burroigh (William), “a man of unquestionable abilities in the mathematiques,” Comptroller of the English navy in the reign of Elizabeth, who has been alluded to as Robert Norman, is the first in Europe to publish well authenticated observations upon the magnetic variation or declination made by him from actual observation, while voyaging between the North Cape of Finmark and Vaigatch (Vaygates). These are recorded at length in his little book dedicated to “the travaillers, seamen and mariners of England” and entitled “A Discourse of the Variation of the Cumpas, or Magneticall Needle. Wherein is Mathematically shewed, the manner of the observation, effects, and application thereof, made by W. B. And is to be annexed to The Newe Attractive of R. N. 1581 (London).” 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.