134 Mr. C. A. Chant on the Variation of Potential along 
oscillation would have a potential loop at each end. But the 
chief minimum shows a rather remarkable variation. As 
the length of the antenna is increased the distance of the 
minimum from the free end increases until it reaches its 
greatest value with a wire 500 cms. long, and then it 
decreases. The reason for this is not very evident, but 
it seems that in this disposition the reaction of the secondary 
of the transformer upon the primary varies with the length 
of the antenna joined to it, thus altering its frequency, the 
greatest change being when the wire is 500 ems. long. 
With an antenna of this length the readings were the highest 
of the series, and the quarter wave-length deduced from the 
curve approximately the same as that obtained in the 
dispositions A, B, C. 
As has been already remarked, the curves are very clearly 
defined. The successive sets of readings agreed remarkably 
well, but yet it was impossible to get a second minimum 
at a distance of three-quarters of a wave-length from the 
end. This is not what was looked for with this transmitter- 
One would expect the condenser circuit, with its persistent 
oscillations, to keep up perfect standing waves in a wire 
in resonance with it, but with no length used was this 
satisfactorily exhibited. 
The waves radiated from the wire, no matter what its 
length, have the frequency of the condenser circuit, and 
also, to a smaller degree, that of the fundamental of the wire. 
Overtones are scarcely noticeable. 
From my experiments it must be concluded that the earth- 
connexion does not injuriously affect the form of the os- 
cillation about the antenna: indeed the curves obtained 
with disposition B are rather more uniform than those with 
the others. The earth-connexion, however, assuredly has 
influence in other ways. I believe all systems of wireless 
telegraphy, except the Braun and the Lodge-Muirhead *, 
join both transmitter and receiver to earth ; and, according 
to Jackson +, severing the earth-connexion reduced the 
signalling distance by 85 per cent. The action of the earth 
must be that of guiding the waves, thus allowing them to 
pass over obstacles such as the bulging-out of the earth’s 
surface. The explanation given by Taylor t seems the most 
satisfactory. 
* See Nature, vol. Ixviil. p..247, July 16, 1903; N.Y. Hlectrical 
World and Engineer, vol. xlii. p. 178, Aug. 1, 1903. 
+ H. B. Jackson, Proc. R. S., lxx. p. 254 (1902). 
t J. E. Taylor, Lond. Electrical Review, May 1899. See also L. de 
Forest, N.Y. Electrical World and Engineer, May 17, 1902; Prasch, 
Die drahtlose Telegraphie (Stuttgart, 1900), p. 65. 
