THE EARTH A MAGNET. 35 



eastern Brazil in one hemisphere, and across Russia, 

 Asiatic Turkey, the Indian Ocean, and West Australia, 

 in the other ; besides having an outlying oval to the 

 east of the Asiatic continent. ~Now these lines have 

 swept round a part of the globe's circuit in a most 

 singular manner since 1600. They have varied alike 

 in direction and complexity. The Siberian oval, now 

 distinct, was in 1787 merely a loop of the eastern line 

 of no declination. The oval appears now to be con- 

 tinually diminishing, and will one day probably dis- 

 appear. 



We find here presented to us a phenomenon as 

 mysterious, as astonishing, and as worthy of careful 

 study, as any embraced in the wide domains of science. 

 But other peculiarities await our notice. 



If a magnetic needle of suitable length be carefully 

 poised on a fine point, or, better, be suspended from a 

 silk thread without torsion, it will be found to exhibit 

 each day two small, but clearly perceptible, oscillations. 

 M. Arago, from a careful series of observations, deduced 

 the following results : 



At about eleven at night, the north end of the 

 needle begins to move from west to east, and having 

 reached its greatest easterly excursion at about a quar- 

 ter-past eight in the morning, returns toward the west 

 to attain its greatest westerly excursion at a quarter-past 

 one. It then moves again to the east, and having 

 reached its greatest easterly excursion at half-past eight 



