EHexperiments of Faraday, Ampére, and Weber. 217 
rotation of the conductor about the magnet. What more, 
may I ask, do we want, or is not this sufficient? Is it to be 
supposed that when the body of the magnet conducts the 
current instead of the insulated sheath, the force of rotation 
of the magnet is then (by some action of the portion of the 
current within the magnet) greater than in the former case, 
i. €. greater than the (converse) force of rotation of the con- 
ductor about the magnet? In other words, when (in the first 
case) the magnet is coated with a sheath (simply to prevent 
the current from entering its body) the rotative forces of the 
magnet and conductor are equal: then (in the second case), 
when the sheath is removed, is it to be assumed, or does Prof. 
Weber’s theory imply, that the opposite rotative forces are 
unequal (so that the magnet and the conductor now tend to 
revolve in opposite directions about each other with unequal 
forces)? It appears that Ampére’s theory is sufficient to 
account for equal rotative forces in magnet and conductor in 
opposite directions. Does Prof. Weber’s view imply that 
unequal forces of torsion—or of tendency to rotation—in 
opposite directions have to be accounted for, or exist when the 
current flows into the body of the magnet ? 
If so, a curious result would appear to follow, viz. (the 
opposite moments of torsion being assumed unequal, or the 
moment of torsion of the magnet on its axis being assumed 
greater than that of the conductor about the magnet) a re- 
sultant moment of torsion must exist inthe system ending to 
turn it about its centre of gravity. Or otherwise expressed, 
it would follow apparently that if the whole system, with a 
small voltaic battery fixed in it, were all delicately suspended 
as one whole, it would tend to rotate about its centre of 
gravity by the action of forces within itself without any 
external visible support or point of reaction. 
I would call attention to this improbable result, which 
appears to follow from Prof. Weber’s view. But l am not 
prepared to contend that this result might not be possible 
under certain conceptions. If found to be true on trying the 
experiment, the result would be highly interesting, as its 
analysis would probably be capable of throwing a light on the 
physical nature of the electric “ current.” 
Another way of trying the experiment might suggest itself. 
The moment of torsion of the magnet on its axis might be 
exactly measured, first with the insulated sheath, and, secondly, 
without it. If in the last case (4. e. without the sheath), the 
moment of torsion were found to be greater, this would (as 
stated) appear to indicate the existence of a resultant moment 
of torsion which, when the sheath is removed, tends to twist 
Phil. Mag. 8. 5. Vol. 19. No. 118. March 1885. Q 
