At p. 150 of the 1869 London edition of Mr. J. F. Nicholl’s “Life of Seb. Cabot” it is said the latter represented to the King of England that the variation of the compass was different in many places, and was not absolutely regulated by distance from any particular meridian; that he could point to a spot of no variation, and that those whom he had trained as seamen, as Richard Chancellor and Stephen Burrough, were particularly attentive to this problem, noting it at one time thrice within a short space. REFERENCES.--Richard Hakluyt, “The Principal navigations, voyages, traffiques and discoveries of the English nation,” 1599: at pp. 237–243, for the voyage of Richard Chancelor, pilote maior, and, at p. 274, for “the voyage of Steuen Burrough, master of the pinnesse called the Serchtrift”; Livio Sanuto, “Geografia,” Venice, 1588, lib. i.; Fournier, “Hydrographie,” lib. xi.; “Library of Am. Biog.,” by Jared Sparks, Boston, 1839, Vols. II and VII as per Index at pp. 318–319; “Jean et Seb. Cabot,” par Hy. Harisse, Paris, 1882; Geo. P. Winship, “The Cabot Bibliography,” London and New York, 1900; Humboldt, “Examen Critique,” Vol. IV. p. 231, and “Cosmos,” Vol. II. (1860) pp. 640, 657–658; Biddle, “Memoir of Seb. Cabot,” 1831, pp. 52–61. =A.D. 1502.=--Varthema-Vertomannus (Ludovico di) leaves Europe for the Indies, as mentioned at p. 25 of his “Travels,” translated by J. Winter Jones, London, 1863, from the original “Itenerario ... ne la India ...” Milano, 1523. He states that the Arabs who navigated the Red Sea were known to have long since made use of the mariner’s chart and compass, and he tells us, in the introduction and at p. 249, that “the captains carried the compass with the needle after our manner,” and that their chart was “marked with lines perpendicular and across.” When the polar star became invisible, they all asked the captain by what he could then steer them, and “he showed us four or five stars, among which there was one (_B. Hydrus_) which he said was opposite to (_contrario della_) our North Star, and that he sailed by the north because the magnet was adjusted and subjected to our north, _i. e._ because this compass was no doubt of European origin--its index pointing to the north, and being unlike that of the Chinese pointing to the south.” REFERENCES.--Cavallo, “Magnetism,” London, 1787, Chap. IV; also, “Hakluyt’s Collection of the early voyages, travels and discoveries,” London, 1811, Vol. IV. p. 547, for “The navigation and voyages of Lewes Vertomannus.” =A.D. 1530–1542.=--Guillen (Felipe), an ingenious apothecary of Seville, and Alonzo de Santa Cruz (who was one of the instructors of mathematics to young Charles V, King of Spain and Emperor of Germany, and the _Cosmografo Mayor_ of the Royal Department of Charts at Seville), construct variation charts and variation compasses by which solar altitudes can be taken.