R. S. HYER MEASUREMENTS OF ELECTRIC WAVES. 
65 
easily located, having an average length of 5.2 meters. With No. 2 the 
work is somewhat more difficult, and the recorded marks are somewhat 
scattered. There is a slight, but decided, increase in the nodal dis- 
tances. With No. 3, having knobs, the work is quite difficult, and the 
record is least satisfactory of all. Yet it is sufficiently distinct to prove 
that the nodes are further apart than with No. 2. We shorten the wire to 
23.5 meters and find that No. 1 does not work so satisfactorily as before, 
yet sufficiently distinct to show that the average distances are about 5.10. 
No. 2 now works unsatisfactorily, and No. 3 does not show any nodes at 
all, the spark going out first at one place and then at another, or not 
going out at all. When the wire is shortened to 23, Nos. 1 and 2 are more 
difficult, the former giving an average' of 5.02. No. 3 has improved 
somewhat, hut now gives only three nodes, with an average of 5.77. 
When the wire is 22 meters, No. 2 likewise drops a node, and after much 
work we decide that No. 1 gives an average length of 4.90. Shortening 
the wire to 21 meters causes No. 1 to drop a node also, their distances 
apart now averaging 5.33. When the wire is further reduced to 20 me- 
ters, the nodes are all clear and sharp, and so continue till the length is 
reduced to 18 meters. Beyond that, Nos, 2 and 3 become difficult; at 
17.5 they are both very unsatisfactory, and at 17.2 we can locate no 
nodes with either; while No. 1, though not so satisfactory, is still doing 
measurable work at distances of about 500. With 17 meters, after much 
labor, we can pick out two nodes with Nos. 2 and 3, the latter placing 
them 5.90 meters' apart, while No. 1 continues to find three at an average 
of 483. With 16.5 meters they are further reduced to 4.73, while with 16 
they are still ill-defined, but now clearly only two in number, with an 
average length of 5.40. With 15, 14, and 13 meters all work beautifully; 
but between 12 and 10 they successively pass through the throes of 
dropping a node. 
So far as I am aware, no other observer has pointed out this dependence 
of nodal distances upon the length of the wire. Hertz, it is true, recog- 
nized the fact that there are certain lengths which best display these 
nodal points, but he erroneously ascribed it to a lack of proper syntony 
with the vibrator. The rule that he lays down for obtaining this syntony 
will not hold good. By this diagram it could be shown that it would in 
a particular case call for one of these critical lengths in which no nodes 
can he found. According to Hertz’s view of the duration of the oscilla- 
tion of the vibrator, we could compare this variation in nodal distances 
and this existence of certain critical lengths without any nodes, to the 
forced vibrations of strings; but it would likewise demand that their ex- 
istence should be detected by only a particular resonator likewise in 
syntony with the vibrator. While the matter has not been fully inves- 
