156 hertz's researches on electrical WAVES/ 



The whole system theu formed a closed metallic circuit, the fimda- 

 meutal vibration of which would have two nodes. Since the period of 

 this vibration would necessarily agree closely with that of each half of 

 the circuit, and therefore with that of the circuit C C, it was to be ex- 

 pected that the vibration would have a pair of loops at the junctions 

 1 and 3, and 2 and 4, and a pair of nodes at the middle points of c d 

 and g h. The vibrations were determined by measuring the sparking 

 distance between the micrometer terminals 1 and 2. It was found that — 

 contrary to what was expected — the addition of the second rectangle 

 diminished this sparking distance from about 3 millimeters to about 1 

 millimeter. The existence of resonant action between the circuit C C and 

 the micrometer circuit was however fully demonstrated, for any altera- 

 tion in the circuit e/*; /«, whether it consisted in increasing or in decreas- 

 ing its length, diminished the sparking distance. It was also found that 

 much weaker sparking took place between c d or g h and an insulated 

 sphere, than between a e or 6/ and the same sphere, showing that the 

 nodes were in c d and g It, as expected. Further, when the sphere was 

 made to touch c d or g h it had no effect on the sparking distance of 1 

 and 2 ; but when the point of contact was at any other portion of the cir- 

 cuit the sparking distance was diminished, showing that these nodes did 

 really belong to the vibration, the resonant action of which increased 

 this sparking distance. 



The wire joining the points 2 and 4 was then removed. As the 

 strength of the induced oscillatory current should be zero at these i)oints, 

 the removal ought not to disturb the vibrations, and this was shown 

 experimentally to be the case, the resonant effects and the position of 

 the nodes remaining unchanged. The vibration with two nodal points 

 was of course not the fundamental vibration of the circuit, which <;on- 

 sisted of a vibration with a node between a and e, and for which the 

 highest values of the potential were at the points 2 and 4. 



When the spheres forming the terminals at these points were brought 

 close together, slight sparking was found to take place between them, 

 which was attributed to the excitation, though only to a small extent, 

 of the fundamental vibration. This explanation was confirmed in the 

 following manner: The sparks between land 2 were broken off, leaving 

 only the sparks between 2 and 4, which measured the intensity of the 

 fundamental vibration. The period of vibration of the circuit C C was 

 then increased by drawing it out to its full length, and thereby increas- 

 ing its capacity, when it was observed that the sparking gradually in- 

 creased to a maximum, and then began to diminish again. The max- 

 imum value must evidently occur when the period of vibration of the 

 circuit G C is the same as that of the fundamental vibration of the 

 micrometer circuit, and it was shown that when the sparking distance 

 between 2 and 4 had its maximum value, the sparks corresponded to a 

 vibration with only one nodal point, for the sparks ceased when the pre- 

 viously existing nodes were touched by a conductor, and the only point 



