84 Mr. R. H. M. Bosanquet on the Magnetic 
There is a slight discontinuity here near the maximum 
value of 4’; but nothing to obscure the general applicability 
of a continuous formula. 
We note that the initial value of yu’, though small, is by no 
means evanescent; that the curve formed by yw’ as ordinate 
and % as abscissa rises very steeply at starting; that p’ 
has a maximum value equal to nearly two thirds of the maxi- 
mum value of mw; and that, although the position of this 
maximum of pg’ is somewhat obscured by the small dis- 
continuity above referred to, yet it is substantially in the 
same position as the maximum of w. 
On the whole, then, the facts are incompatible with those 
with which Weber’s theory and Maxwell’s modification of it 
are framed to correspond; and it will be of interest to 
consider whether there be any hypothesis by which these facts 
can be represented. 
Prof. Hughes has recently put forward a theory, the funda- 
mental supposition of which appears to be identical with that 
of the theory of Weber; but I cannot find that it has been 
applied so as to give any quantitative account of magnetizing 
functions or permeabilities. 
I will now give an illustration of the suppositions as to 
molecular magnets, which would have to be made, in order 
that the principal term of the permeability may be propor- 
tional to the sine of an angle whose zero corresponds ap- 
proximately to the zero of magnetic induction, and 180° to 
saturation, the angle being proportional to magnetic induc- 
tion in between. The resulting theory is of an impossible 
character. 
Let a typical molecule be represented by a small magnet 
hung by a torsion-wire at the centre of a coil, and let the 
magnet be placed so that when no current is passing it 
stands nearly at right angles to the plane of the coil, but 
with the poles in the opposite direction to that which the 
action of the coil tends to make them assume. Suppose, then, 
that a current is sent through the coil; the needle will be 
deflected, and will rest at the point where the deflecting 
couple on the needle is balanced by the torsion of the 
wire. Now the couple due to the coil may be expressed as 
GC sin @; where C is the current, G a constant, and @ the 
deflection from a position at right angles to the coil. The 
torsion may be represented by 7(@—e), where « is small; or 
approximately by 7@, whence we have for the position of 
rest 
TO=GC sin 0. 
