658 COSMOS. 



were continually beset by a host of impracticable proposals. 

 Sebastian Cabot, as we learn from his friend, Richard Eden, 

 boasted on his death-bed, of having had a " divine revelation 

 made to him of an infallible method of finding geographical 

 longitude." This revelation consisted in a firm conviction 

 that magnetic declination changed regularly and rapidly with 

 the meridian. The cosmographer, Alonso de Santa Cruz, 

 one of the instructors of Charles V., undertook, although cer- 

 tainly from very imperfect observations, to draw up the first 

 general variation chart* in the year 1500, and, therefore, 

 one hundred and fifty years before Halley. 



The advance or movement of the magnetic lines, the know- 

 ledge of which has generally been ascribed to Gassendi, was 

 not even conjectured by William Gilbert, although Acosta, 

 " from the instruction of Portuguese navigators," had at a much 

 earlier period assumed that there were four lines without decli- 

 nation over the earth's surface.f No sooner was the dipping- 

 needle invented in England, in 1576, by Robert Norman, 

 than Gilbert boasted that, by means of this instrument, he 

 could determine a ship's place in dark starless nights (aere 

 calignoso).\ Immediately after my return to Europe I showed 



* In corroboration of this statement regarding Sebastian Cabot on 

 his death-bed, see the well written and critically historical work by 

 Biddle, entitled A Memoir of Sebastian Cabo, (p. 222). " We do not 

 know with certainty," says Biddle, " neither the year of the death or 

 the burying place of the great navigator who gave to Great Britain 

 almost an entire continent, and without whom (as without Sir Walter 

 Raleigh,) the English language would perhaps not have been spoken by 

 many millions who now inhabit America." On the materials according 

 to which the variation chart of Alonzo de Santa Cruz was compiled, as 

 well as on the variation-compass, whose construction allowed alti- 

 tudes of the sun to be taken at the same time, see Navarrete, Noticia 

 biogranca del cosmografo Alonso de Santa Cruz, pp. 3-8. The first 

 variation-compass was constructed before 1525, by an ingenious apothe- 

 cary of Seville, Felipe Guillen. The endeavours to learn more exactly 

 the direction of the curves of magnetic declination were so earnest, that, 

 in 1585, Juan Jayme sailed with Francisco Gali from Manila to Aca- 

 pulco, merely for the purpose of trying in the Pacific a declination in- 

 strument which he had invented. See my JJssai politique sur la 

 Nouvelle Espagne, t. iv. p. 110. 



t Acosta, Hist, natural de las Indias, lib. i. cap 17. These four 

 magnetic lines without variation led Halley, by the contests between 

 Henry Bond and Beckborrow, to the theory of four magnetic poles. 



$ Gilbert, de Magnete Physiologia nova, lib. v. cap. 8. p 200. 



