the Lines of Magnetic Force. 413 



the gain of intensity in the former case may be produced, but 

 there is none as yet distinctly recognised. Like electric currents, 

 side by side, add their quantities together ; a case supplied either 

 by uniting several batteries by their like ends, or comparing a 

 large plate battery with a small one. Like magnetic lines of 

 force do the same (323.2.). 



3269. The mutual relation of the magnetic lines of force and 

 the electric axis of power has been known ever since the time of 

 (Ersted and Ampere. This, with such considerations as I have 

 endeavoured to advance, enables us to form a guess or judgement, 

 with a certain degree of probability, respecting the nature of the 

 lines of magnetic force. I incline to the opinion that they have 

 a physical existence correspondent to that of their analogue, the 

 electric lines ; and having that notion, am further carried on to 

 consider whether they have a probable dynamic condition, ana- 

 logous to that of the electric axis to which they are so closely 

 and, perhaps, inevitably related, in which case the idea of mag- 

 netic currents would arise ; or whether they consist in a state of 

 tension (of the ?ether ?) round the electric axis, and may there- 

 fore be considered as static in their nature. Again and again 

 the idea of an electro-tonic state (60. 1114. 1661. 1729. 1733.) 

 has been forced on my mind ; such a state would coincide and 

 become identified with that which would then constitute the 

 physical lines of magnetic force. Another consideration tends 

 in the same direction. I formerly remarked that the mag- 

 netic equivalent to static electricity was not known ; for if the 

 undeveloped state of electric force correspond to the like unde- 

 veloped condition of magnetic force, and if the electric current 

 or axis of electric power correspond to the lines of magnetic force 

 or axis of magnetic power, then there is no known magnetic con- 

 dition which corresponds to the static state of the electric power 

 (1734.). Now assuming that the physical lines of magnetic 

 force are currents, it is very unlikely that such a link should be 

 naturally absent ; more unlikely, I think, than that the magnetic 

 condition should depend upon a state of tension ; the more espe- 

 cially as, under the latter supposition, the lines of magnetic 

 power would have a physical existence as positively as in the 

 former case, and the curved condition of the lines, which seems 

 to me such a necessary admission, according to the natural facts, 

 would become a possibility. 



3270. The considerations which arise during the contempla- 

 tion of the phsenomena and laws that are made manifest in the 

 mutual action of magnets, currents of electricity, and moving 

 conductors (8084. &c.)j arc, 1 think, altogether in favour of the 

 physical existence of the lines of magnetic force. When only a 

 single magnet is employed in such cases, and the use of iron or 



