548 
ME. G. GOEE ON ELECTEOTOESION. 
and the others gave only traces of effect. 2nd. After a down ward current, six coil 
ones, producing north poles below, were transmitted : the first gave a movement of 
5*25 mm. to the right hand, and the others scarcely any effect. The downward current 
being restored several times, six coil ones, producing south poles below, were passed : 
the first produced a movement of 5*5 mm. to the left hand, and the others scarcely 
any effect. 
These results may be compared with those obtained with the same wire and battery- 
current, and described in Section 17, page 540. 
To ascertain whether in these cases a portion of the residual axial-current influence 
still remained in the steel, I passed an axial current down a steel wire in the helix, 
and then a series of ten currents through the coil, each producing a north pole below. 
The first coil one produced a movement of 3*5 mm. to the right hand, and the others 
only minute torsions. On now passing an opposite current through the coil, a move- 
ment of 4 mm. to the left hand took place, proving that the axial influence still 
remained. 
30. Relative values of residuary effects of opposite coil-currents and of axial ones in 
producing torsion. 
Several of the series of experiments already described have shown that the magnitude 
of the first torsion produced by a current is specially liable to be affected by various 
mechanical and magnetic conditions of the axial wire or rod, which may be very readily 
overlooked, and is therefore only a very crude measure of the amount of residuary effect 
of a previous current. 
In order, therefore, to obtain more precise knowledge respecting the relative amounts 
of residuary effect of opposite concurrents I transmitted two series of such currents, 
and passed, in the interval of time between each current, in the first series a momentary 
upward axial one, and in the second series a downw ard one ; and to obtain similar 
information respecting opposite axial currents I passed two series also of them, and in 
the space of time between each current transmitted in the first series a momentary coil 
one, producing a north pole below, and in the second series one producing a south pole. 
In all the experiments the iron wire employed was 1*75 mm. thick, and had no weight 
attached to it ; and the electric current was from twelve cells arranged as three. 
The following are the results tabulated, and the determinations in each series num- 
bered in the order in which they were made. The capital letters indicate the kind of 
polarity of the lower end of the wire, the vertical arrows show the direction of the 
axial current, the horizontal ones that of the movements of the index, and the decimal 
numbers their magnitudes ; the variations in these numbers in each vertical column 
arose chiefly from the difficulty of getting the pointer perfectly steady. A rigid appa- 
ratus, and a firm foundation for its support, are highly necessary in cases where the 
torsions require to be accurately measured. 
The lower end of the wire was a weak south pole at the commencement of the expe- 
