VARIATION CHARTS. 55 



From the remarks which I have already made, there can 

 scarcely be a doubt that the general application of the mag- 

 netic needle by Europeans to oceanic navigation as early as 

 the 12th century, and perhaps even earlier in individual cases, 

 originally proceeded from the basin of the Mediterranean. 

 The most essential share in its use seems to have belonged 

 to the Moorish pilots, the Genoese, Venetians, Majorcans, 

 and Catalans. The latter people, under the guidance of 

 their celebrated countryman, the navigator, Don Jaime Fer- 

 rer, penetrated, in 1346, to the mouth of the Rio de Ouro 

 (23° 40' N. lat.), on the western coast of Africa; and, ac- 

 cording to the testimony of Raymundus Lullus (in his nauti- 

 cal work, Fenix de las Maravillas del Orbe, 1286), the Barce- 

 lonians employed atlases, astrolabes, and compasses, long be- 

 fore Jaime Ferrer. 



The knowledge of the amount of magnetic variation is of 

 a very early date, and was simultaneously imparted by the 

 Chinese to Indian, Malay, and Arabian seamen, through 

 whose agency it must necessarily have spread along the 

 shores of the Mediterranean. This element of navigation, 

 which is so indispensable to the correction of a ship's reck- 

 oning, was then determined less by the rising and setting of 

 the sun than by the polar star, and in both cases the determ- 

 ination was very uncertain ; notwithstanding which, we find 

 it marked down upon charts, as, for instance, upon the very 

 scarce atlas of Andrea Bianco, which was drawn out in the 

 year 1436. Columbus, who had no more claim than Sebas- 

 tian Cabot to be regarded as the first discoverer of the vari- 

 ation of the magnetic needle, had the great merit of determ- 

 ining astronomically the position of a line of no variation 

 2^-° east of the island of Corvo, in the Azores, on the 13th 

 of September, 1492. He found, as he penetrated into the 

 western part of the Atlantic Ocean, that the variation pass- 

 ed gradually from northeast to northwest. This observation 

 led him to the idea, which has so much occupied navigators 

 in later times, of finding the longitude by the position of the 

 curves of variation, which he still imagined to be parallel to 

 the meridian. We learn from his ship's log that when he 

 was uncertain of his position during his second voyage 

 (1496), he actually endeavored to steer his way by observ- 

 ing the declination. The insight into the possibility of such 

 a method was undoubtedly that uncommunicable secret of 

 longitude which Sebastian Cabot boasted on his death-bed 

 of having acquired through special divine manifestation. 



