An Account of the Caufe of the Change 

 of the Variation of the Magne- 

 tical Needle, with an Hypothecs 

 of the StruBure of the Internal 

 Parts of the Earth ; as it was pro* 

 pofed to the Royal Society in one 

 of their late Meetings. By Mr 4 

 Edmund Halley. 



HAving in \ the precedent Difcourfe deli- 

 vered a Theory of the Variation of the 

 Magnetical Compafs, wherein I did collecT: as 

 many Ob/ervations as at that time I eould 

 procure, and having carefully compared them 

 together, I came at length to this general 

 conclufion, That the Glebe of the Earth might 

 be fuppofed to be one great Magnet, having four 

 "Magnetical Poles or Paints of AttraBion, near 

 each Pole of the Eauator two ; and that in thofe 

 farts of the World which lie near adjacent to 

 any one of thofe Magnetical Poles, the Needle . is 

 chiefly govern d thereby j the near eft Pole being al- 

 ways predominant ever the more remote. And I 

 there have endeavour'd to ftate and limit the 

 prefent Pofition of thofe Poles in the Surface of 

 our Globle, which the Reader pleafing to con- 

 fult, will fave us the pains of repeating. But 

 after all, tho' that Difcourfe was favourably 

 receiv'd both at home and abroad, as feeming 

 Jo render a tolerable account of the obferv'd 



Variations 



