ME. G. GOEE OjN t ELECTEOTOESION. 
553 
with the fact that a suitably powerful coil-current at once removes and reverses the 
residuary longitudinal magnetic polarity in a soft iron wire, but only gradually removes 
the residual effect of an axial current, and does not at all reverse it (see Section 27). 
Each axial current also transmits its own characteristic influence through several 
subsequent coil-current changes, and each coil-current similarly through axial-current 
changes, in a kind of hereditary manner. 
34. The condition produced in iron and steel by an axial current. 
The experiments generally described in this paper show conclusively that the mag- 
netism produced in iron by an axial-electric current is distributed very differently from 
that in a cross section of an ordinary electromagnet ; it also arises from an influence 
within the iron, whereas the latter is produced by one from without. They also show 
that the phenomenon of electrotorsion is essentially magnetic, and strongly support 
the view that the state existing in iron when an electric current is passing axially 
through it, upon which the torsion depends, is not the transverse magnetism of the 
current itself, and which is inseparable from it (see Section 24, page 545), but that 
induced in the iron by the current, because electrotorsion does not occur in non- 
magnetic metals (see Section 4), and because the residuary axial-current state is destroyed 
by a red heat (see Section 24). 
I have not made any experiments to ascertain whether the effect of an axial current 
can be communicated at a distance from one piece of iron to another by mere proximity 
or contact ; nor have I examined whether the same condition can be acquired by vibrating 
a demagnetized iron rod at right angles to the terrestrial magnetic meridian*. 
35. Torsions produced by simultaneous coil- and axial currents. 
Several modifications of this method were examined : — 1st, with undivided currents ; 
2nd, with divided ones; and 3rd, with one current passed temporarily during the con- 
tinuance of the other, &c. ; and in each case torsions were freely produced. The second 
and third of these arrangements were the best. 
There was a special difference between the torsions produced by alternate currents 
and those yielded by simultaneous ones. In the former case, on cessation of the current, 
the pointer only slightly returned towards zero, and the wire remained twisted (except 
in a limited number of special instances, see Section 20, p. 542, and Section 32) ; 
on repeating the current in the same direction, only the small elastic torsions occurred, 
and the large movements in the same direction could only be again obtained by reversing 
the current, and then again repeating it in the original direction. But with the two 
currents flowing simultaneously, on stopping them the index returned nearly to zero, 
* About the year 1777 Beccakia noticed “ that a needle, through which he had sent an electric shock, had 
in consequence acquired a curious species of polarity ; for, instead of turning as usual to the north and south, 
it assumed a position at right angles to this, its two ends pointing to the east and west.” — Eo get’s (s Treatise 
on Electromagnetism,” page 3, in * Library of Useful Knowledge,’ 1832. 
MDCCCLXXIV. 4 E 
