130 Mr. C. A. Chant on the Variation of Potentiat along 
That at 1000 ems. is not decisive from the curve, and so it 
is omitted in the following calculation (though including 
it would make no difference in the result) :— 
Aj2=-: 2x 130 =2607ems: 
=425—130=295_ ,, 
=(15—425=290 
Mean 282. ,, 

These, I believe, are half wave-lengths of overtones. Inthe 
first case the wire was grounded and so only odd overtones 
would be possible, the one present being probably the ninth, 
counting the fundamental the first. If such was the case, 
‘the entire length of the oscillating wire from free end to 
earth should be 
249 
2 
a result requiring the oscillator to be equivalent to 
1120—(1000+ 75), or 45 cms. 
of the wire. This explanation seems to me the most probable. 
I may remark that the curves obtained with the wire 
1000 ems. long, connected to earth, were the most irregular 
of all secured during the investigation, especially in the 
space between 100 and 300 cms. from the free end. A 
possible cause contributing to this may have been that the 
electrical disturbance was not produced immediately at 
the earth end. 
In the second case the oscillating wire was free at each 
end, and so the entire system of overtones was possible. 
The one present, with half wave-length of 282 cms., seems 
to be the fourth, in this case the oscillator adding to the wire 
one-fourth of a wave-length. | 
It may be questioned why these particular overtones were 
present, and the others not noticeable. I think it was 
because the natural period of the oscillator alone was in 
approximate accord with them, being about one-half that of 
those exhibited. This would agree with the results of 
Lindemann*, who found that the waves proper to the 
oscillator as well as those of the entire system of oscillator 
and wires should be present. 
I have not been able to identify the other ripples of the 
curves. 
Slaby + and Braun { have both studied the simple Marconi 
* A, Lindemann, Ann. der Physik, 11. p. 376 (1900). 
+ A. Slaby, Elektrotechnische Zeitschrift, 1902, p. 168; extended 
abstract in Lond. Electrician, vol. xlix. p. 6 (1902). 
¢ F. Braun, Phys. Zeitschrift, iii. p. 143 (1900). 
OX 
=1120 cms., 

