Miftellanea Curiofa, 4.9 



The Period of this Motion being wonderful 

 great, and there being hardly an hundred Years 

 Snce thefe Variations have been duly obferv'd, 

 it will be very hard to bring this Hypothecs to 

 a Calculus, efpecially fmce, though the Varia- 

 tions do increafe and decreafe regularly in the 

 fame place, yet in differing places, at no great 

 diftance, there are found fuch cafual Changes 

 thereof as can no ways be accounted for by a 

 regular Hypothecs ; as depending upon the un- 

 equal and irregular diftribution of the Mag- 

 netical Matter within the Subftance of the Ex- 

 ternal Shell or Coat of the Earth, which de- 

 flect the Needle from the Pofirion it would ac- 

 quire from the effect: of the general Magnetifm 

 of the whole, Of this the Variations at London 

 and Paris give a notable Inftance, for the Needle 

 has been con ftantly about more Eafterly at 

 Parts than at London ; though it be certain that 

 according to the general effect, the Difference 

 ought to be the contrary way : Notwithstanding 

 which, the Variations in both places do change 

 alike. 



Hence, and from fbme other of like Nature, 

 I conclude, That the two Poles of the External 

 Globe are nxt in the Earth, and that if the 

 Needle were wholly govern'd by them, the Va- 

 riations thereof would be always the feme, with 

 fbme little*Irregularities upon the account I but 

 juft now mention'd : But the Internal Sphere 

 having fuch a gradual tranflation of its Poles, 

 does influence the Needle, and direct it vari* 

 oufly, according to the refult of the attractive 

 or directive Power of each Pole ; and cons- 

 equently there rauft be a Period of the Revolu- 

 tion of this Internal Ball, after which the Va- 

 riations wiH return again as before. But if it 

 E lhall 



