=A.D. 1555.=--Olaus Magnus, a native of Sweden and Archbishop of Upsala (where he died during 1568) issued in Rome his great work “Historia de Gentibus Septentrionalibus,” which, for a long time, remained the chief authority on Swedish matters. In this book, Gilbert says (“De Magnete,” lib. i. cap. 1) allusion is made to a certain magnetic island and to mountains in the north possessing such power of attraction that ships have to be constructed with wooden pegs so that as they sail by the magnetic cliffs there be no iron nails to draw out. To this, reference is made by Thos. Browne (“Pseud. Epidem.,” 1658, Book II. p. 78) as follows: “Of rocks magnetical, there are likewise two relations; for some are delivered to be in the Indies and some in the extremity of the North and about the very pole. The Northern account is commonly ascribed unto Olaus Magnus, Archbishop of Upsala, who, out of his predecessors--Joannes, Saxo and others--compiled a history of some Northern Nations; but this assertion we have not discovered in that work of his which commonly passeth among us; and should believe his geography herein no more than that in the first line of his book, where he affirmeth that Biarmia (which is not 70 degrees in latitude) hath the pole for its zenith, and equinoctial for the horizon.” In a Spanish book entitled “The Naval Theatre,” by Don Francisco de Seylas and Louera, we find two causes assigned for the variation of the declination; one is “the several mines of loadstones found in the several parts of the earth ...” the other being that “there is no doubt but large rocks of loadstones may affect the needles when near them ...” (“Philos. History ... Roy. Acad. Sc. at Paris,” London, 1742, Vol. II. pp. 279–280). REFERENCES.--Claudus Ptolemæus, “Geographia,” lib. vii. cap. 2 (and others named by Bertelli Barnabita at foot of p. 21 of his “Pietro Peregrino de Maricourt,” Roma, 1868, viz. Klaproth, “Lettre sur la Boussole,” Paris, 1834, p. 116; Thos. H. Martin, “Observ. et Théor. des anciens,” Rome, 1865, p. 304; Steinschneider, “Intorno. alla calamita,” Roma, 1868); also Albertus Magnus, Lugduni, 1651; Mr. (Thomas) Blundeville, “His Exercises”; Fracastorio, in the seventh chapter of his “De Sympathia et Antipathia”; F. Maurolycus, “Opuscula,” 1575, p. 122a; Lipenius, “Navigatio Salomonis Ophiritica”; Paulus Merula, “Cosmographia Generalis,” Leyden, 1605; Toussaincte de Bessard, “Dialogue de la Longitude,” Rouen, 1574; U. Aldrovandi, “Musæum Metallicum,” 1648, pp. 554, 563, wherein he alludes to the magnetic mountains spoken of by Sir John Mandeville; Ninth “Encycl. Brit.,” Vol. XVII. p. 752; also the entry at A.D. 1265–1321.