ME. G. GOEE ON ELECTEOTOESION. 
557 
experiment simultaneously) or reversed, nor if the two acting currents were made to 
commence simultaneously. 
The residuary state preceding these instances was not manifested by a conspicuous 
degree of permanent twist; in the first case that amounted to 1*5 mm., and in the 
second to only *25 mm. ; this, however, agrees with constant experience in the subject: 
a non-magnetized iron wire is not visibly twisted by a powerful coil-current (or axial 
one) alone, but acquires an invisible potent condition which reveals itself by torsion on 
the subsequent passage of suitable currents. I have not examined why these exceptions 
to the law occur only in cases where a downward axial current is employed. 
These peculiar instances, together with the various other phenomena of electrotorsion 
and detorsion, support the view that the molecular mechanism of iron is a complex 
one ; they also illustrate the very great influence which the order of succession of the 
currents exerts in some cases, and to which attention has already been called (see 
Section 20, page 543). 
40. General influence of the order of succession of the currents. 
A general review of the phenomena described in this paper shows that the hereditary 
action and order of succession of the various currents affects the torsions in all cases ; 
in all it affects the direction and apparently also the magnitude, in a less number of 
cases it causes detorsion to occur, and in a very few instances it enables torsion to be 
produced in the opposite direction to the fullest extent. 
41. Relative magnitudes of torsional effect of electric currents during jmd after 
their passage. 
Whilst making the experiments on the magnitudes of the torsions produced by alter- 
nate coil- and axial currents (described in Section 20), I made a series of other experi- 
ments with the same iron wire (*. e. T75 mm. diameter and without any weight attached 
to it) and arrangement of battery, but passing one current during the continuance of 
the other, for the purpose of obtaining some idea of the relative magnitudes of residuary 
torsional influence of the two currents to that of their torsional power during their 
circulation in the coil and axial wire : — 
(A) With the coil-current continuous and the axial one temporary.— 1 . With south 
pole below and a downward current and also with an upward one. 2. With a north 
pole below and a downward axial current and with an up ward one. 
(B) With the axial current continuous and the coil one temporary. — 1 . With a north 
pole below and a downward axial current and with an upward one. 2. With a south 
pole below and an upward axial current and with a downward one. 
Each single experiment was repeated. The magnitudes of the whole of the tor- 
sions varied from 19 to 24 mm., and averaged 22’4 mm. In the other experiments 
referred to, the average magnitude of all the torsions produced by coil-currents was 
