THE CONQUEST OF THE ZONES 



been further perfected by attaching the needle to a cir- 

 cumferential card on which the* ^points of the compass," 

 thirty-two in number, were permanently marked. At 

 all events the compass card had been so divided before 

 the close of the fourteenth century, as is proved by a 

 chance reference by Chaucer. The utility of the in- 

 strument thus perfected — ^indeed its entire indispensa- 

 bleness — was doubtless by this time clearly recognized 

 by all navigators; and one risks nothing in suggesting 

 that without the compass no such hazardous voyage 

 into the unknown as that of Columbus would ever have 

 been attempted. 



No doubt the earliest observers of the needle believed 

 that it pointed directly to the North. If such were 

 indeed the fact the entire science of navigation would be 

 vastly simpler than it is. But it required no very acute 

 powers of observation to discover that the magnetized 

 needle does not in reality point directly towards the 

 earth's poles. There are indeed places on the earth 

 where it does so point, but in general it is observed 

 to deviate by a few degrees from the exact line of the 

 meridian. Such deviation is technically known as 

 magnetic declination. That this declination is not the 

 same for all places was discovered by Columbus in the 

 course of his first transatlantic voyage. 



A century or so later, the accumulated records made 

 it clear that declination is not a fixed quantity even at 

 any given place. An Englishman, Stephen Burrows, is 

 credited with making the discovery that the needle 

 thus shifts its direction slightly with the lapse of time, 

 and the matter was more clearly determined a little 



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