XXIII. On some Electromagnetic Experiments, continued.— 
No. Il. Diverse views of Faraday, Ampere, and Weber. 
By 8. Totver PREsTon*. 
N Poggendorff’s Annalen (1841, Bd. lii.) is a remarkable 
paper by Prof. W. Weber, entitled “ Die unipolare 
Induction,” which refers of course to the well-known fact of 
the induction of continuous currents by the influence of the 
single pole of a rotating magnet. 
In spite of the comparatively old date of this paper, it is 
well known and referred to in the present day. This paper 
has some relation to the subject of my last communica- 
tion to the Philosophical Magazine (February 1885) ; but I 
wish to point out that it does not alter or affect the conclu- 
sions there arrived at, but, on the contrary, tends to confirm 
them. 
The paper of Prof. Weber appears to open out a new ques- 
tion, distinct from the phenomena dealt with in my commu- 
nication ; and I would call attention to the fact that Prof. 
Weber’s idea would appear to involve one theoretie conclusion 
which appears at first sight improbable, but which, if true, 
would seem to render an experimental determination possible 
which might be capable of throwing some light on the phy- 
sical nature of the electric “current.”” Iam not aware that 
the subject has been considered from this point of view, and 
of course anything I submit will be open to criticism. 
I will remark, first, that Prof. Weber agrees with my view 
(which accords with that of Ampére, and is opposite to that of 
Faraday), viz. that the “ lines of force,”’ or field of force, about 
a magnet must be considered in that sense fixed or dependent 
on the magnet, that this field of force rotates when the mag- 
net rotates on its axis, or, otherwise put—When a magnet 
rotates on its axis, the field of force must (in regard to the 
inductive effect) be considered as moving with the magnet 
and intersecting external conductors, in the same selse as it 
would do if the magnet were bodily translated. 
The chief point which I wish to notice in Prof. Weber’s 
paper is his view as to the cause of the rotation of a magnet 
* Communicated by the Author. 
+ I may mention that the object of my last paper was to point out an 
apparent ambiguous case (involving an oversight) in Faraday’s experi- 
ments, which caused him to take the opposite of the above view as to the 
rotation of the field of force with the magnet, whereby Faraday contradicted 
_ Ampére’s theory in this respect, although he speaks in approving terms 
of the theory in other respects. 
