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XIV. On the Norlh-tvesl Magvelic Pole. By Colonel 



NSummeriand-place, Exeter, Dec. 15. 

 o event will be deemed more remarluible by I'uture ages, than 

 the decided discovery of the actual existence of a north-west 

 magnetic pole, by the haidv and enterprising navif>ators of the 

 passing century. The vast importance of the fact is of the ut- 

 most consequence, as it must, infallibly, in time, lead to certain 

 theory of the difference of the variations of the magnetic needle. 

 Dr. Halloy had recourse to tlic supposition of (our magnetic 

 poles belonging to a magnetic nucleus revolving within the earth, 

 from east to west ; and thus he attempted to accmnt for the 

 variation, and its clianges, supposed to have been first observed 

 ])y Columbus and Sebastian Cabot. Euler, under a very plaus/i- 

 bie and ingenious theory, supposed only two magnetic poles. 

 Mr. Churchman adopted the idea of two magnetic poles ; and 

 imagined the northern one to move eastward, on a parallel of 

 latitude, while the southern moved slower ; the former taking 

 1096 veais in its revolution, while the latter required 2289. The 

 r.orth-west pole was supposed by these philosophers to be situated 

 not far from where the recent discovery has placed it. The de- 

 flection of the needle has been found by the navigators in the dis- 

 covery ships, to have exceeded one-fourth of a great circle. Cap- 

 tain Cook in his voyages approached nearly, in the south hemi- 

 sphere, to the supposed situations of the south magnetic poles, 

 and found no qnunfuvL of variation that could at all sanction the 

 supposition of their actuality. This certainly furnishes strong 

 evidence that these poles are more imaginary than real ; and 

 tl'.at all future theories of variation must, necessarily, be deduced 

 from the well-known attraction of the north and south poles of 

 the earth, combined with the ascertained action of the north- 

 west n)agnetic pole, whose positive discovery reflects so much 

 credit on the present age. This is still further confirmed by a 

 general remark to be made on the variations oi Cook; viz. that 

 in southern latitude particularly, they were, in east and west 

 longitude, of opposite descriptions, and decidedly influenced, re- 

 latively, by the magnetic pole, whose position is now nearly 

 knovwi. Had the southern poles existed, the approximation to 

 their imagined situations, Ijy several circun)navigalor«,must,from 

 the known lavvs of magnetism, have given rise to so strong an 

 attraction of the south end of the magnetic needle, as would have 

 made the variation three time*!, at least, greater than it has 

 proved ; independent of causing it to be of a different nature 

 from what actually appears in the records of voyages. — Thus, 

 then, this interesting subject seems to be reasonably cleared from 



* From The Gentleman's Magazine for December 1820. 



the 



