ME. G. GORE ON ELECTROTORSION. 
555 
circumstances (see Section 20, page 542), it will be seen that simultaneous currents 
leave less residual effect than single ones. 
Simultaneous and divided currents, on the first time of passing, produced a loud and 
dull sound on making contact, and a weaker and more metallic one on breaking contact, 
but by each repetition in the same direction the reverse, and their first passage produced 
louder sounds than their repetitions. 
37. Influence of relative strength of the two currents. 
As the magnitude of the torsions produced by simultaneous currents depends upon 
both currents, and is therefore limited by the weakest, the two currents must be pro- 
perly proportioned to each other in order to produce the maximum degree of torsion. 
To effect that object, I have increased the strength of the axial current and decreased 
that of the coil one (or vice versa), until, after passing and stopping the two simulta- 
neously, a small sign of residual axial-current effect was detected by torsion produced 
on passing a single current through the coil only. The best proportion of the two 
forces, with the apparatus and iron wire (2‘6 m. long and T75 mm. diameter) I usually 
employed, was the current from four cells arranged as two for the coil, and that 
from eight arranged as four for the axial wire. By actual measurement it was found 
that the electric conduction-resistance of the helix in that apparatus (see Section 1) 
was equal to -309 ohm, and that of the iron wire 2*6 m. long and 1-75 mm. diameter 
was equal. to T37 ohm; therefore with two batteries of equal power attached to the 
coil and iron wire respectively, the quantity of electricity passing through the axial 
wire was two and a quarter times the amount of that circulating through the coil ; and 
with eight cells attached to the axial wire and four to the coil, the difference would of 
course be double that amount. 
The torsional effects produced by simultaneous and undivided currents passing through 
the bar and helix in one continuous circuit were similar to those described in Section 36, 
but were comparatively small, evidently in consequence of the electric power being dis- 
advantage ously applied, the axial wire requiring a relatively much greater current. 
38. Influence of metal screens. 
A brass tube 2*6 m. long and 11-5 mm. external diameter was fixed in the helix, 
with the soft iron wire 1*75 mm. diameter suspended in its axis, and the battery divided 
into two portions of six cells each. By arranging each six cells as three, and trans- 
mitting the two currents simultaneously, deflections varying from 18'5 to 23‘5 mm. took 
place, showing that the brass tube did not materially intercept the torsional influence 
of the coil-current. In some similar experiments, in which a thin iron tube was employed 
instead of the brass one, diminution of torsion occurred. 
4 e 2 
