the Lines of Magnetic Force. 417 



dium, for they form continuous curves like those I have imagined 

 within and without the magnet. The direction of these lines of 

 electric force may be traced, experimentally, many ways. A mag- 

 netic needle freely suspended in the fluid will show them in and 

 near to the battery, by standing at right angles to the course of 

 the lines. Two wires from a galvanometer will show them ; for 

 if the line joining the two ends in the fluid be at right angles 

 to the lines of electric force (or the currents), there will be no 

 action at the galvanometer ; but if oblique or parallel to these 

 lines, there will be deflection. A plate, or wire, or ball of 

 metal in the fluid will show the direction, provided any electro- 

 lytic action can go on against it, as when a little acetate of lead 

 is present in the medium, for then the electrolysis will be a max- 

 imum in the direction of the current or line of force, and nothing 

 at all in the direction at right angles to it. The same ball will 

 disturb and inflect the lines of electric force in the surrounding 

 fluid, just as I have considered the case to be with paramagnetic 

 bodies amongst magnetic lines of force (2806. 2821. 2874.). 

 No one I think will doubt that as long as the battery is in the 

 fluid, and has its extremities in communication by the fluid, lines 

 of electric force having a physical existence occur in every part 

 of it, and the fluid surrounding it. 



3277. I conceive that when a magnet is in free space, there is 

 such a medium (magnetically speaking) around it. That a va- 

 cuum has its own magnetic relations of attraction and repulsion 

 is manifest from former experimental results (2787.) ; and these 

 place the vacuum in relation to material bodies, not at either 

 extremity of the list, but in the midst of them, as, for instance, 

 between gold and platina (2399.), having other bodies on either 

 side of it. What that outer magnetic medium, deprived of all 

 material substance, may be, I cannot tell, perhaps the aether. I 

 incline to consider this surrounding or outer medium as essential 

 to the magnet ; that it is that which relates the external polari- 

 ties to each other by curved lines of power ; and that these must 

 be so related as a matter of necessity. Just as in the case of the 

 battery above, there is no line of force, either in or out of the 

 battery, if this relation be cut off by removing or intercepting 

 the conducting medium, or in that of static electric induction, 

 which is impossible until this related state be allowed (1169.)*; 

 so in like manner I conceive, that without this external mutually 

 related condition of the poles, or a related condition of them to 

 other poles sustained and rendered possible in like manner, a 

 magnet could not exist ; an absolute northness or southness, or an 

 unrelated northness or southness, being as impossible as an abso- 

 lute or an unrelated state of positive or negative electricity (1178.). 



* Philosophical Magazine, March 184.'*; or Experimental Researches, 

 8vo, vol. ii. p. 279. 



Phil. Mag. S. 4. Vol. 3. No. 20. June 1852. 2 E 



