552 
MR. G. GORE ON ELECTROTORSION. 
would differ from the corresponding left-hand one only by a reverse direction of its con- 
current ; but in that case the magnitudes would be unsymmetrical. 
32. Apparently exceptional cases of torsion. 
The directions of the torsions given in the two columns headed “ S ” on page 550 
disagree with those shown by the figures in Class B, Plate XLII. (see Section 18), 
and apparently contradict the law stated in Section 6. On examining the notes of the 
experiments they were, however, found, like those described in Section 20, page 542 
(see also Section 21), to be cases not of torsion, but of detorsion ; they coincide also 
with the instances of decrease of magnitude of movement noticed in Section 30, 
page 551, and Section 31. Why a coil-current producing a south pole below should 
behave thus in cases where it followed an axial one which was preceded by a similar 
coil one, and not in those where the axial one was preceded by a dissimilar coil one 
(see Section 30, p. 549), and why such a phenomenon does not occur with a coil- 
current which produces a north pole below (see Section 30, page 550), I have not 
investigated. These detorsions are, however, probably dependent upon the influence 
of terrestrial magnetism, because they do not occur when the south pole is above. 
As real torsion and detorsion can only he detected and measured by the aid of a 
proper zero-point, it is necessary to have the wire well annealed and free from mag- 
netism and mechanical twist before commencing a series of experiments, and not to 
disturb the zero-point by mechanical motion of the apparatus. A very effectual way to 
remove the residual effects of both coil- and axial currents is to heat the rod or wire to 
redness in a direction at right angles to the magnetic meridian, and allow it to cool in 
that position without disturbing it (see Section 24). A more convenient but less perfect 
way is to repeatedly and simultaneously pass a coil-current producing a south pole below, 
and an axial one of proper relative strength (see Section 37, page 555), and stop the two 
currents simultaneously ; the pointer will then settle very near zero, and the wire will 
only possess the usual magnetism induced by terrestrial influence (see Section 35). 
33. Coexistence of the coil-current and axial-current states in iron and steel. 
The two conditions, or rather directions, of magnetic condition were observed to co- 
exist in the same wire in many of the experiments. All rods or wires of iron or steel 
in which there remained the effect of an axial current were at the same time in a more 
or less longitudinally magnetic state by the influence of terrestrial magnetism, and could 
then be twisted by the application either of a suitable coil-current or of an axial one. 
These properties may, however, be also interpreted according to the view already given 
(see Section 5, p. 532), that in all wires of iron under such circumstances the axes of the 
molecules lie in a spiral direction with regard to the axis of the wire, and are therefore 
in a position to be moved by the influence either of a longitudinally or tangentially 
magnetizing force. 
The view that the two conditions are to some extent distinct and independent agrees 
