90 On the North-west Magnetic Pole. 



A small needle compared to a large real magnet, is experimentally 

 found to furnish a similar effect to a magnetie compass-card, 

 acted on bv some invisible magnetic power within the body of 

 the earth. This leads to the certain conclusion, that the changes 

 in variation, and those much less in dip, arise from a correspond- 

 ing change or movement in the cause. I have made the remarks 

 contained in this paper,'because I am led to believe that the recent 

 discovery of a north-west magnetic pole has put it in the power 

 of experimental philosophy to establish, in time, the law of move- 

 ment of the magnetic cause producing effects which have hitherto 

 baffled all human research. The anomalies of the variation ob- 

 served by different persons in the same year, in London, clearly 

 evince that the application of a needle to a meridian-line accu- 

 rately laid down, can alone furnish the precise variation at the 

 place of observation. — In two papers by me, in the Philosophical 

 Transactions for 1796 and 1798, the process of laying off such a 

 meridian is described ; and this was done for the purpose of as- 

 certaining accurately, not only the variation, but also the varia- 

 tion oj' the variation,, or the diurnal vibrating variation, at Ben- 

 coolen or Sumatra ; and afterwards, at the island of St. Helena. 

 Professor Gillebrand first noticed this diurnal variation in 1635. 

 This vibrating variation moves and returns through a few mi- 

 nutes of a degree, daily ; and in different places its direction and 

 quantity do not correspond. Many theories have been formed, 

 in order to account for this extraordinary magnetic phasnome- 

 non; and the experiments made by the application of heat to 

 magnets, afford, probably, the most ])lausible solution of the 

 case: but a series of accurate observations on meridians, in many 

 distant situations, are requisite to remove serious objections lying 

 against the best-imagined of these conjectural theories. 



From the dip of the needle it is quite unquestionable that the 

 magnetic power, or cause, lies at some unknown depth under 

 the surface of the earth. Mr, iEpinus, of the Imperial Academy 

 of St. Petersburgh, has distinctly traced the close and intimate 

 analogy between magnetism Hud electricity : and the Galvanic 

 experiments lately made by the prince of chemists. Sir Humphry 

 Davy, place the fact beyond all doubt. Experiments show that 

 a subtle fluid of these united descriptions pervades the atmo- 

 sphere, andiron, magnetised and otherwise; forming a constant 

 and invisible communication between the magnetic cause within 

 the earth and common magnetic needles. There is now every 

 reason to conclude, that the aurora horealis constitutes a mag- 

 netic current between the real north pole and the north-west 

 magnetic pole; the one giving out to the other an excess of 

 fluid, in order to restore an equilibrium between positive and 

 negative quantities. This supposition may not be quite gratu- 

 itous, 



