546 
ME. G-. GOEE ON ELECTEOTOESION. 
magnitudes of movement of the pointer were as follows : — 1st, 2*25 mm. ; 2nd, -hsk T5 ; 
3rd, 1-0 ; 4th, 0’5 ; and 5th, 0’5. 
(2) After an up ward one . — Four alternately opposite currents were passed, the first 
producing a south pole below. The movements were: — 1st, 2-25; 2nd, T75; 
3rd, 0-5 ; and 4th, 0-5. A series of alternately opposite coil-currents, therefore, 
gradually removes the residual effect in an iron wire of an axial current in either 
direction. 
On comparing these results with those described on page 538 it appears that it re- 
quired more persistent treatment to remove the residual effect of a coil-current than 
that of an axial one, probably partly because the influence of terrestrial magnetism 
assisted in maintaining the former and in removing the latter. 
If we assume that the first torsion in each of these two sets of experiments was, to 
some extent, a measure of the residuary effect of the axial current, we find that in iron 
the magnitudes of residuary effect of a downward axial current and of an upward one 
were equal. 
As a series of coil-currents only gradually removes the residual effect of axial ones, 
and a series of axial currents only very gradually changes the ordinary magnetic polarity 
of iron and steel (see Sections 16 & 28), the degree of persistency of those residuary 
conditions must be remembered whilst making experiments in electrotorsion. 
It is probable that the longitudinally magnetizing power of terrestrial magnetism, like 
that of a coil-current, would also remove the residual effect of an axial current if the 
axis of the iron was in the terrestrial magnetic meridian and sufficient time was allowed, 
especially if vibration was also applied. 
Although it requires a series of alternately opposite axial currents to remove the 
residual effect of a coil one, and a number of alternately reversed coil-currents to re- 
move that of an axial one, a single opposite coil-current, also a single opposite axial 
one, each of sufficient power, respectively produce those effects. It would appear from 
this that the two states produced by opposite coil-currents (or axial ones) are incom- 
patible and cannot coexist, and that a coil-current acts in a more mechanically advan- 
tageous way in obliterating the effect of an opposite coil-current than in removing that 
of an axial one ; and an axial current acts more effectively in effacing the influence of 
an opposite axial one than in reversing or removing that of a coil one. Further inves- 
tigation of the phenomena in a mechanical aspect, and of the relations of the torsions to 
mechanical changes, electric sounds, expansion by heat, &c., may possibly disclose a 
glimpse of the relative directions of the molecular movements produced in iron by the 
two kinds of currents. 
28. Effect of coil-currents upon residuary axial-current influence in steel. 
These experiments were similar to those in Section 27. The wire was 2 - 6 m. long 
and 2T6 mm. diameter, and the same battery-current employed as before. 
(1) After passing a down ward axial current. — Fourteen coil-currents, alternately 
