ME, Q. GOEE ON ELECTEOTOESION. 
550 
weight appeared to have a strong effect in modifying and diminishing the magnitude of 
the torsions under the headings D and E. 
44. Comparison of magnitudes of the torsions generally in iron and steel. 
I obtained the torsions with these two substances under nearly similar conditions. 
The diameter of the iron wire was 3 mm. and of the steel 2 ’7 mm., and no weight 
was attached to either. The electric current was from twelve Geove’s cells, and was. 
applied in each of the following ways : — 
1st. Alternately reversed axial currents only , and the twelve' cells arranged as three. — ■ 
The torsions obtained with iron averaged 5 - 4 times the magnitude of those with steel; 
they varied from 3*25 to 3*5 mm. with iron, and from *5 to '75 mm. with steel. 
2nd. Alternately reversed coil-currents . — The movements were 2 -55 times as large 
with the steel as with the iron ; their magnitudes varied from ’5 to 1 mm. with the 
iron, and from 1*5 to 2 - 33 mm. with the steel. 
3rd. Alternate axial and coil-currents , in every possible order. — The magnitude of 
the movements obtained with iron averaged T77 time that of those obtained with steel; 
those with iron varied from 1 to 5'5 mm., and those with steel from *0 to 4 mm. 
Several cases of detorsion occurred in this series. 
4th. Simultaneous coil- and axial currents . — The current from six cells arranged as 
three was used with the coil, and a similar current with the axial wire, and the two 
currents were commenced and stopped simultaneously. Every possible combination 
of the two currents, and every order of succession (twelve in number) of each pair of 
them, was tried. The movements obtained with iron averaged 2-42 times the magni- 
tude of those produced with steel. The magnitudes of those with iron varied from 
575 to 16’25 mm., and with steel from -25 to 7 - 75 mm. 
The results of these four classes of experiments show that, except with alternately 
opposite coil-currents succeeding an axial one, iron is much better adapted than steel 
for producing large electrotorsions. 
[It is probable that the generally smaller torsions obtained with steel than with iron 
was partly due to the greater degree of mechanical resistance which that substance 
offers to torsion, and partly to its differences of magnetic properties and chemical com- 
position. Electrotorsion therefore affords prospectively a new method of investigating 
the mechanical and magnetic properties, and the chemical composition, of magnetic 
metals.] 
45. Is the voltaic coil twisted during experiments of electrotorsion \ 
Some experiments were made of passing currents from the twelve cells arranged as 
six through a loose spiral, 630 mm. long and 16 mm. outer diameter, of thick copper 
wire, fixed at its upper end and surrounding a fixed cylindrical rod of soft iron 640 mm. 
long and 10 mm. thick, the lower end of the coil being free and provided with a pointer 
3 80 mm. long. Torsional movements amounting to 7 mm. (as well as the well-known 
