OCEANIC DISCOVERIES. 279 



between 1111 and 1117, that the mode of measuring the 

 amount of western declination had long been understood. The 

 merit due to Columbus is not to have made the first observa- 

 tion of the, existence of magnetic variation, since we find, for 

 example, that this is set down on the chart of Andrea Bianco 

 in 1436, but that he was the first who remarked, on the 13th 

 of September, 1492, that " 2|- east of the island of Corvo the 

 magnetic variation changed and passed from N.E. to N.W." 

 Tkis discovery of a magnetic line vAthout variation marks 

 a memorable epoch in nautical astronomy. It was celebrated 

 with just praise by Oviedo, Las Casas, and Herrera. We 

 can not assume, with Livio Sanuto, that this discovery is due 

 to the celebrated navigator, Sebastian Cabot, without entirely 

 losing sight of the fact that Cabot's first voyage, made at the 

 expense of some merchants of Bristol, and distinguished for its 

 success in reaching the continent of America, was not accom- 

 plished until five years after the first expedition of Columbus. 

 The great Spanish navigator has not only the merit of having 

 discovered a region in the Atlantic Ocean where at that period 

 the magnetic meridian coincided with the geographical, but 

 also that of having made the ingenious observation that mag- 

 netic variation might likewise serve to determine the ship's 

 place with respect to longitude. In the journal of the second 

 voyage (April, 1496) we find that the admiral actually de- 

 termined his position by the observed declination. The diffi- 

 culties were, it is true, at that period still unknown, which 

 oppose this method of determining longitude, especially where 

 the magnetic lines of declination are so much curved as to 

 follow the parallels of latitude for considerable distances, in 

 stead of coinciding with the direction of the meridian. Mag- 

 on terrestrial magnetism, William Gilbert, who can not be supposed to 

 have had the slightest knowledge of Chinese literature, should regard 

 the mariner's compass as a Chinese invention, which had been brought 

 to Europe by Marco Polo. " Ilia quidem pyxide nihil unquam humaiiis 

 excogitatum artibus humano generi profuisse magis, constat. Scientia 

 uauticas pyxidulae traducta videtur in Italiam per Paulum Venetum, qui 

 circa annum mcclx. apud Chinas artem pyxidis didicit." {Gulielmi 

 Gilberti Colcestrensis, Medici Londinensis de Magnete Physiologia nova, 

 Tjond., 1600, p. 4.) The idea of the introduction of the compass by 

 Marco Polo, whose travels occurred in the interval between 1271 and 

 1295, and who therefore returned to Italy after the mariner's compass 

 had been mentioned as a long-known instrument by Guyot de Provins 

 in his poem, as well as by Jacques de Vitry and Dante, is not sup- 

 ported by any evidence. Before Marco Polo set out on his travels in 

 the middle of the thirteenth century, Catalans and Basques already 

 made use of the compass. (See Raymond Lully, in the Treatise Dt 

 Contemplatione, written in 1272.) 



