176 hertz's researches on electrical waves. 



secondary couductors previously described. The existence of station- 

 ary waves showed that the waves in the rectilinear wire were of a 

 steady character in space as well as in time. The nodal points were 

 determined in the following manner: The further end of the wire was 

 left free, and the secondary conductor was brought near to it, in such 

 a position that the wire lay in its plane, and had the air space turned 

 towards it. As the secondary was moved along the wire, points of no 

 sparking were observed to recur periodically. The distance from the 

 point n to the first of these was measured, and the length of the wire 

 made equal to a multi[)le of this distance. The experiments were then 

 repeated and it was found that the nodal points occurred at approxi- 

 mately equal intervals along the wire. 



The nodes could also be distinguished from the loops in other ways. 

 The secondary conductor was brought near ro the wire, with its plane 

 perpendicular to it, and with its air space neither directed completely 

 towards the wire nor completely away from it, but in au intermediate 

 position, so as to produce e. m. f.'s perpendicular to the wire. Sparks 

 were then observed at the nodes, while they disappeared at the loops. 

 When sparks were taken from tlie rectilinear wire by means of an in- 

 sulated conductor, they were found to be stronger at the nodes than at 

 the loops ; the difference however was small, and was indeed scarcely 

 distinguishable unless the position of the nodes and loops was previ- 

 ously known. The reason that this and other similar methods do not 

 give a well-defined result lies in the fact that irregular oscillations are 

 superposed upon the waves considered ; the regular waves however 

 can be picked out by means of the secondary, just as definite notes are 

 picked out b}' means of a Helmholtz resonator. If the wire is severed 

 at anode, no effect is produced ujion the waves in the portion of wire 

 next to the origin ; but if the severed portion of wire is left in its place, 

 the waves continue to be propagated through it, though with somewhat 

 diminished strength. 



The possibility of measuring the wave-lengths leads to various appli- 

 cations. If the copper wire hitherto used is replaced by one of differ- 

 ent diameter, or by a wire of some other metal, the nodal points retain 

 their position unchanged. It follows from this that the velocity of prop- 

 agation in a wire has a definite value independent of its dimensions and 

 material. Even iron wires offer no exception to this, showing that the 

 magnetic susceptibility of iron does not play any part in the case of 

 such rapid motions. It would be interesting to investigate the behavior 

 of electrolytes in this respect. In their case we should expect a smaller 

 velocity of propagation, because the electrical motions are accompanied 

 by motions of the molecules carrying the electric charges. It was found 

 that no propagation of the waves took place through a tube 10 millimeters 

 in diameter, filled with a solution of sulphate of copper; but this may 

 have been due to the resistance being too high. By the measurement 

 of wave-lengths the relative vibration periods of different primary con- 



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