VARIATION OF THE COMPASS. 



THE deviation of the magnetic needle from its 

 parallel with the meridian, or east or west from 

 the true north and south points. 



Progressive Motion of the Variation. 



In 1576, about the time when this phenomenon 

 was first remarked, the variation was found to be 

 11 15' E., consequently at that time a ship to sail 

 due north, found it necessary to steer north by west. 



Although the variation of the compass when first 

 discovered was only 11 15' E.-, there can be little 

 doubt that about A.D. 2040, it will again be as much 

 east as it is now west. In A. D. 1662 the variation 

 in London was nothing. 



Discovery of the Variation of the Compass. 



The first discovery of the variation of the compass 

 is by some ascribed to Columbus, by others to Sebas- 

 tian Cabot. That it was discovered so late in .Europe 

 and not at all in China, where the compass had been 

 longer known, may be accounted for from this circum- 

 stance, that in Europe it was then very small, and 

 in China for these two or three hundred years, in 

 some places nothing, and no where more than two 

 degrees. 



Retrogradation of the Variation. 



In the rooms of the Royal Society the mean varia- 

 tion in June, 1817, was ' 24 17' 54" West. 

 In June, 1818, - - 24 17 

 In June, 1819, - - 24 15 43 



