540 
ME. G-. GOEE ON ELECTEOTOESION. 
the others gradually diminished to 0*5 mm. After restoring the south polarity by a 
coil-current, ten axial currents were passed up it. The first torsion was 6*5 mm. to the 
right hand, the second 1*5 mm., and the others T25 mm. In each of these two series 
the torsions after the first one were largely due to the renewal of the longitudinal 
magnetism by terrestrial influence. 2. With a north pole below, six downward 
currents were transmitted: the first produced a movement of 3*75 mm. to the right 
hand, and made the lower end of the wire neutrally magnetic to a compass-needle, and 
the following ones yielded no movement. After restoring the same polarity by means 
of the coil-current, six upward currents were passed : the first produced a deflection of 
2-5 mm. to the left , and rendered the lower end of the wire a feeble south pole ; the 
second 06 to the right hand, the 3rd TO to the right, and the remainder the same. 
B. In a steel wire 2T7 mm. diameter. — 1. With a south pole below, produced by 
the coil-current, six downward currents were first passed. The first of them produced 
a movement of 5'5 mm. to the left hand, and the subsequent ones yielded no torsions. 
The polarity was then restored by means of the coil-current, and six axial currents in 
succession then passed upwards. The first gave a deflection of 3*25 mm. to the right 
hand, the second -25, and the others no movement. 2. With a north pole below, 
six downward currents were first transmitted; the first of them gave a torsion of 
5'5 mm. to the right hand, and the succeeding ones had no effect. After restoring the 
polarity as before, six upward currents were passed : the first produced a movement of 
6’25 mm. to the left hand, and the others had no visible effect. 
The sudden cessation of torsion after the first current in steel, and the much more 
gradual cessation of it in iron, are quite conspicuous. The fact that the magnitudes of 
the first torsions, both in iron and steel, are smaller with a north pole below than with 
a south one, agrees with the view that the magnitude of the movements depends upon 
that of the residuary longitudinal magnetism. 
To ascertain whether in such experiments as these some of the longitudinal mag- 
netism remained after the first axial current had passed, although no torsion was 
produced by the subsequent axial currents, I transmitted through the coil (containing 
a steel wire) a current producing a south pole below, then passed 10 axial currents in 
succession down the wire ; only the first one produced torsion. On then transmitting 
a current up the wire, a torsion occurred, proving that the magnetic effect of the coil- 
current still remained. 
18. Will a previous axial current enable a coil-current to produce torsion \ 
To ascertain also if the previous passage of an axial current conferred upon the iron 
the capacity of being twisted by a coil one, I passed a current from the 12 cells in one 
series up the bar of 11 mm. diameter, then through the helix several times, making the 
lower end of the bar a south pole ; then up the bar again, and then several times through 
the coil, producing a north pole ; and I repeated this series of experiments, employing 
a current down the bar. In each case th e first application of the coil-current produced 
