Geology and Magnetism. 



495 



and the South end is the repulsive, or in plainer language, that the 

 magnetic fluid or currents move towards the north, enter into the 

 axis, through which they pass, then issue out from the south pole 

 and encircle the globe to complete their circuit (as indicated by the 

 direction of the needles, and illustrated by the arrows in the follow- 

 ing sketch) ; — we ought to be able to trace their effects on all sub- 

 stances within the limits of our observations. 



If the earth be a magnet, as we have endeavoured to prove, it 

 must produce the effects observed ; if it be not a magnet, it possess- 

 es a property identical in its results to one ; therefore all we re- 

 quire in our investigations is the knowledge of the law of these ac- 

 tions, as the name of the primary cause of the action cannot have 

 a material influence on our researches. If we continue to call 

 it gravitation, we must add to it a property which was not applied 

 to it before, viz. polarity, — call \t magnetism, and the term embraces 

 all we require in astronomy as well as in geology. 



Let us suppose a bar, having been made magnetic, to be placed 

 in the axis of an artificial globe, if iron filings be strewed care- 

 fully over it, the filings would become magnetic, and arrange 

 themselves in curves like the magnetic needles on our globe, as 

 shown in Plate I.* The small magnetic ingredients do not converge 

 to one mathematical point at each end of the bar, but to a space 

 equal to the transverse section of the axis ; and if this effect is 

 produced by a current of subtile fluid, which may be conceived 

 to emanate from one pole and to enter in at the other, penetrating 

 * As above. — Ed. 



