1883.] Theory of Magnetism based on New Researches. 107 



apart from, molecular rotation, which has changed the spiral direction 

 of the electric current ? The answer to this is most clear — that it is 

 entirely due to molecular rotation. If the wire is perfectly neutral, 

 we obtain by the current of one half-pint bichromate cell 45° deflec- 

 tion of the needle to the left for a left-handed torsion, and a similar 

 degree to the right for a right-handed torsion, depending altogether 

 upon the softness of the iron for the degree of force obtained, but in 

 all cases perfectly equal on each side. If we magnetise the wire so 

 that it produces about 45 u to the right, then a torsion to the right 

 produces no effect whatever; the molecules have already rotated to 

 the degree which mechanical torsion could produce, and torsion aided 

 by the electric current can produce no further rotation. The left-hand 

 torsion, however, preserves its full maximum effect, and restores the 

 molecules to their previous position. If again we magnetise the wire 

 to saturation, so that the needle is violently moved to the right, 

 having 80° or more deflection, then the right-band torsion, instead of 

 augmenting it, instantly reduces the deflection to 45°, being the 

 maximum allowed by a right-handed torsion. We have here, in the 

 case of an electric spiral, decreased effects from an increased me- 

 chanical torsion in the same direction, and the experiment clearly 

 shows the rotation of the molecules independent of mechanical direc- 

 tive action. 



Being desirous of noticing the effects of powerful electric currents, 

 Dr. Warren De La Rue, F.R.S., kindly aided me by passing a current 

 from his well-known chloride of silver battery through iron and steel 

 wires. A condenser, 42 '8 microfarad capacity, charged by 3,360 cells, 

 was used. We first passed this enormous electric charge longitudinally 

 through the permanent magnet I have described, fig. 5, completely 

 destroying its evident polarity by rotating the molecules to neutrality. 



This experiment was followed by discharging the condenser through 

 magnetised and neutral steel knitting needles with a similar result. 

 Many authors have stated that a steel wire or needle became mag- 

 netised by the charge from a Leyden jar, and as this is contrary to the 

 neutrality I have spoken of, we continued the experiments with a view 

 to determine the conditions of such magnetic effects. We have found 

 that the magnetisation supposed to be the result of the electric spark 

 is in reality due to the direction in which the needle lies at the time of 

 the passage of the spark. Thus wires, when held perpendicular to the 

 magnetic meridian, or east and west, became perfectly neutral, even 

 when previously strongly magnetised ; but if they were held in the 

 magnetic meridian, a feeble magnetism was always produced, the 

 direction of which was due entirely to the earth's polarity, and had no 

 relation whatever with the direction of the current. If, however, the 

 wires were twisted, as in a rope, then we had electromagnetic effects, 

 due to the direction of the twist and current. 



