supposed Polarity of Diamagnetic Bodies. 89 



in the magnetic field, are polar or not, is however an exceed- 

 ingly important question ; and very essential and great differ- 

 ences, in the mode of action of these bodies under the one 

 view or the other, must be conceived to exist. I found that 

 in every endeavour to proceed by induction of experiment 

 from that which is known in this department of science to the 

 unknown, so much uncertainty, hesitation and discomfort 

 arose from the unsettled state of my mind on this point, that 

 I determined, if possible, to arrive at some experimental proof 

 either one way or the other. This was the more needful, 

 because of the conclusion in the affirmative to which Weber 

 had come in his very philosophical paper; and so important 

 do I think it for the progress of science, that, in those imper- 

 fectly developed regions of knowledge, which form its boun- 

 daries, our conclusions and deductions should not go far be- 

 yond, or at all events not aside from the results of experiment 

 (except as suppositions), that I do not hesitate to lay my pre- 

 sent labours, though they arrive at a negative result, before 

 the Royal Society. 



2642. It appeared to me that many of the results which 

 had been supposed to indicate a polar condition, were only 

 consequences of the law that diamagnetic bodies tend to go 

 from stronger to weaker places of action (2418.) ; others again 

 appeared to have their origin in induced currents (26. 2338.) ; 

 and further consideration seemed to indicate that the differ- 

 ences between these modes of action and that of a real pola- 

 rity, whether magnetic or diamagnetic, might serve as a foun- 

 dation on which to base a mode of investigation, and also to 

 construct an apparatus that might give useful conclusions and 

 results in respect of this inquiry. For, if the polarity exists it 

 must be in the particles and for the time permanent, and 

 therefore distinguishable from the momentary polarity of the 

 mass due to induced temporary currents; and it must also 

 be distinguishable from ordinary magnetic polarity by its 

 contrary direction. 



2643. A straight wooden lever, 2 feet in length, was fixed 

 by an axis at one end, and by means of a crank and wheel 

 made to vibrate in a horizontal plane, so that its free extre- 

 mity passed to and fro through about two inches. Cylinders 

 or cores of metal or other substances, 5± inches long and 

 three-quarters of an inch diameter, were fixed in succession 

 to the end of a brass rod 2 feet long, which itself was attached 

 at the other end to the moving extremity of the lever, so that 

 the cylinders could be moved to and fro in the direction of 

 their length through the space of 2 inches. A large cylinder 

 electro-magnet was also prepared (2191.), the iron core of 



