278 ■ COSMOS. 



possessions, at i distance of one hundred miles to the west of 

 the Azores. 1£ we consider further that Columbus, imme- 

 diately after his return from his first voyage of discovery, pro- 

 posed to go to Home, in order, as he said, to " give the pope 

 notice of all that h3 had discovered," and if the importance 

 attached by the cotemporaries of Columbus to the discovery 

 of the line of no variation be further borne in mind, it will be 

 admitted that I was justified in advancing the historical prop- 

 osition that the admiral, at the moment of his highest court 

 favor, strove to have a "^?A?/Sica^ line of demarkation con- 

 verted into a 2^oUtical oneT 



The influence which the discovery of Am.erica and the 

 oceanic enterprises connected with that event so rapidly ex- 

 orcised on the combined«mass of physical and astronomical 

 science, is rendered most strikingly manifest when we recall 

 the earliest impressions of those who lived at this period, and 

 the extended range of those scientific eflbrts, of which the 

 more important are comprehended in the first half of the six- 

 teenth century. Christopher Columbus has not only the mer-. 

 it of being the first to discover a line without magnetic va 

 7'iation, but also of having excited a taste for the study of 

 terrestrial magnetism in Europe, by means of his observations 

 on the progressive increase of western declination in receding 

 from that line. The fact that almost every where the ends 

 of a freely-moving magnetic needle do not point exactly to 

 the geographical north and south poles, must have repeatedly 

 been recognized, even with very imperfect instruments, in the 

 Mediterranean, and at all places where, in the twelfth centu- 

 ry, the declination amounted to more than eight or ten de- 

 grees. But it is not improbable that the Arabs or the Cru- 

 saders, who were brought in contact wuth the East between 

 the years 1096 and 1270, might, while they spread the use 

 of the Chinese and Indian mariner's compass, also have drawn 

 attention to the northeast and northwest pointing of the mag- 

 netic needle in difierent regions of the earth as to a long- 

 known phenomenon. We learn positively from the Chinese 

 Fenthsaoyan, which was written under the dynasty of Song,* 



marks graven in rocks, or by the erection of towers. It is commanded, 

 " que se liaga alguna senal 6 torre," that some signal or tower be erect- 

 ed wherever the dividing meridian, whether in the eastern or the west- 

 ern hemisphere, intersects an island or a continent in its course from 

 pole to pole. In the continents, the rayas were to be marked at pi'op« 

 er intervals by a series, of such marks or towers, which would indeed 

 have been no slight undertaking. 



*' It appears to be a reiuvvkable fact, that the earliest classical writef 



