Experiments of Faraday and Pliicker.-~° =: 187 
Moreover, it seems very apparent on consideration that 
when the above double magnet rotates, its lines of force must 
rotate with it. For imagine one of the two magnets (which 
form the compound bar) to be removed. Then the centre of 
gravity of the other will now lie outside the axis of rotation. 
Therefore this magnet and therefore its lines of force will (by 
the rotation) be bodily translated about the axis. For Fara- 
day himself admits that when a magnet (or its centre of 
gravity) is translated, its lines of force accompany it, and 
would intersect and inductively affect external conductors. 
The same reasoning now applies to both magnets (if the other 
be brought back), so that when the whole revolves the lines 
of force of each bar (and therefore of the whole) are translated 
about the axis, 7.e. revolve with the magnet (or compound 
bar), and would influence external conducting bodies. This 
must, I think, be sufficiently clear; indeed, by holding a 
sheet of paper with loose iron filings horizontally above the 
end of the compound bar, one could, no doubt, in a certain 
sense, see the movement of the lines of force by observing the 
small disturbances produced in the iron filings, as the irre- 
gularities in shape or magnetic distribution of the poles pass 
under the filings when the compound bar revolves. This 
must be obvious enough, and it will probably be thought 
superfluous to carry the analysis of this point further. For 
we are concerned here only with one single oversight (depend- 
ing on a double or ambiguous aspect in the experiments); 
and as soon as Faraday, in the first instance, thought his 
view warranted or necessitated by the experimental results, 
he, of course (consistently), applied it throughout, and so a 
considerable number of experiments are affected. My object 
is only to reach the truth, and, whatever it may be, we shall 
certainly gain by its recognition. 
As regards the experiments of Pliicker, although the 
various forms of apparatus specially constructed by him for 
the determination of this and related questions is generally 
more complicated than the apparatus of Faraday, yet it is 
easy to see on going through the drawings that the same 
oversight, viz. the neglect of the influence of the galvano- 
meter wires (or the external galvanometer-loop circuit) on 
the results, affects all his experiments alike; so that 1 deem 
it unnecessary to consider these experiments further here. 
They are described very completely in the paper in Poggen- 
show that these (currents) are perfectly equal to each other” (p. 33). 
My contention is that this experiment preves nothing, although there 
may be independent grounds for concluding that the lines of force outside 
the magnet are equal in power to those znside. 
Phil. Mag. 8. 5. Vol. 19. No. 117. Feb. 1885. L 
