Mifcellanea Curiofa. 4 1 



Thus, I hope, 1 have not loft my Pains 

 and Study in this difficult Subject ; believing 

 that I have put it paft doubt, That there are in 

 the Earth four fuch Magnetical Points nr Potes% 

 which occafion the great variety andfeeming irregu? 

 larity which is obfervd in the Variations of tie 

 Cctnpdfs. But to calculate exactly what it is, 

 in any place affign'd, is what I dare not yet 

 pretend to, though I could wifh it were my hap- 

 pinefs to be able to oblige the World with fo 

 ufeful a piece of Knowledge ; there are Diffi- 

 culties that occur, that render the thing as yet 

 not feafible ; for firft there are a great many 

 Obfervations requifite, which ought to be made 

 at the feme time ; not at Sea, but aftiore, with 

 greater Care and Attention than the generali- 

 ty of Sailors apply. And hefides, it remains 

 undetermined in what proportion the attractive 

 Power decreafes, as you remove front the Pole 

 of a Magnet, without which it were a vain 

 attempt to go about to calculate. There is yet 

 a further Difficulty, which is the Change of the 

 Variation, one of the Difcoveries of this laft 

 Century ; which (hews, that it will require fome 

 hundreds of Years to eftablifh a compleat Do- 

 ctrine of the Magnetical Syftem. From the 

 foregoing Table k fhou Id feem, that all the 

 Magnetical Poles had a motion Weftward : 

 But if it be fb, 'tis evident, that it is not a Ro- 

 tation about the Axis of the Earth ; for then 

 the Variations would continue the Tame, in the 

 fame parallel of Latitude (the Longitude only 

 chang'd) as much as is the motion o£ the Mag- 

 netical Poles, but the Contrary is found by Ex- 

 perience j for there is no where in the Latitude 

 of i yi North between England and America, a 

 Variation of eleven Degrees Eaft at this time ; 



