Intelligence and Miscellaneous Articles. 519 



electromotive force is a quadratic sine-function of the time, and 

 impulses are produced in the conductor in only one direction. Cal- 

 culation gives the result, that while the electromotive force varies 

 between zero and a maximum value, the momentary current -strength 

 is always different from zero, and varies periodically between a 

 minimum and a maximum value. The mean current- strength is 

 independent of the self-induction and has always the same value, 

 whether the self-induction of the conductor is very large or is equal 

 to zero. The self-induction causes no loss of mean current-strength ; 

 its action only consists in making the waves plane. .Formulae are 

 given for the mean square of the current- strength, and for the work 

 developed in the circuit, from which formulae it can be seen that 

 the magnitudes adduced depend on the displacement of phase, and 

 satisfy the law of the superposition of the actions of two com- 

 ponents of electromotive force. In conclusion the analogy is 

 pointed out which exists between the laws investigated of elec- 

 trical flow and those of the rotatory motion of a heavy wheel 

 under the action of successive mechanical impulses. — Wiener 

 Bcvichte, April 23, 1891. 



OX WHEATSTONE S DETERMINATION OF THE VELOCITY OF 

 ELECTRICITY. BY PROF. J. STEFAN. 



In the paper on the Motion of Electricity iu Wires, Kirchhoff in 

 1857 first showed that in certain conditions electricity moves in a 

 thin wire according to the laws of wave-motion, and with a velocity 

 which can be put equal to that of light. The agreement between 

 the velocities of electricity and of light only holds, however, when 

 electricity travels in a straight wire stretched in the air. Kirch- 

 hoff restricted his investigation to this case. If we apply the 

 bases of his calculation to other cases, for instance, a wire which 

 is bent backwards and forwards in zigzag or is wound in a spiral, 

 it is found that electricity travels under these conditions with a 

 far greater velocity. 



In Wheatstone's well-known method twenty plane windings of 

 drawn-out wire were used, and the velocity of electricity was found 

 by this measurement to be half as much again as that of light. 

 In the preceding I think I have given the correct explanation of 

 this result. I have, however, also attempted to give this explana- 

 tion an experimental basis, and for this purpose I have employed 

 the method given by Hertz of producing stationary electrical waves 

 in wires. ] have used a similar conductor to that of Wheatstone, 

 but on a smaller scale, and connected it with a couple of long 

 straight wires, and compared the length of a wave in the conductor 

 with the length of the same wave in the straight wires. The wave 

 in the conductor is considerably longer, and in accordance with 

 this the velocity of electricity in the conductors is greater than in 

 the straight wires, and, according to my experiments, in a ratio which 

 still exceeds that found by Wheatstone. — Wiener Berichte, April 23, 

 1891. 



