in Magnetism and Electricity. 91 



conditions, would involve the idea of the miraculous or the 

 paradoxical. 



36. In expcrimentino; with the magneto-electric machine, it 

 was found that the dead point of the armature, or that position 

 during its revolution in which no electricity is evolved, varied 

 with the length or the resistance of the wires which joined the 

 poles of the machine. It therefore became necessary to change 

 the position of the commutator on the armature-axis to suit the 

 different circuits through which the electricity was transmitted, 

 so that the burning effects of the spark at the junction of the 

 two halves of the commutator might be avoided when the direc- 

 tion of the current was changed. 



37. When the commutator was properly adjusted to the resist- 

 ance of the wires surrounding the electromagnet (33), I observed 

 that so long as the magneto-electric machine was allowed to run 

 without its poles being connected, either with the wires of the 

 electromagnet or any other conductor, a brilliant star of light 

 appeared at the points where the springs were in contact with 

 the commutator (15) \ but when the poles of the machine were 

 connected by means of a short piece of wire, the bright light at 

 the commutator instantly disappeared. It was also observed 

 that when the poles of the machine were connected with the 

 long helices of the large electromagnet, a perceptible interval of 

 time elapsed before the light at the commutator disappeared. 

 Besides this, it was also observed that at the moment of breaking 

 contact between the wires of the electromagnet and the poles of 

 the machine, a much more brilliant spark appeared at the points 

 of separation, and a much more severe shock was felt when the 

 body formed part of the circuit, than could be produced by the 

 direct action of the machine alone. The latter effects could not, 

 however, be obtained until a certain interval of time had elapsed 

 after contact had been made between the electro-helices and the 

 wires of the machine. 



38. Moreover I found that a spark could be obtained from 

 the wires surrounding the electromagnet even after they had 

 been entirely disconnected from the machine. This curious 

 result was obtained by first holding the free extremities of the 

 wires surrounding the electromagnet, one in each hand, in con- 

 tact for a few seconds with the respective polar terminals of the 

 machine, and, while contact was still maintained, bringing the 

 ends of the electrohelices into metallic contact with each other, 

 so that they formed a continuous metallic loop or closed circuit. 

 The loop so formed was then suddenly removed from the polar 

 terminals, and while thus entirely disconnected from them the 

 ends of the loop were suddenly separated, and a bright spark 

 appeared at the point of disjunction. With a larger and more 



