the Transmitting Antenna in Wireless Telegraphy. 135 
This explanation is very similar to that suggested by 
Lecher *, and to that by Heaviside t. More recently 
Kopsel { has put forward the view that in Marconi’s long- 
distance transmission the earthing wire and earth capacity 
form a system in partial, if not in entire, resonance with the 
antenna. There may have been some such effect in the 
transatlantic experiments, but such can hardly be the case in 
the numerous experiments by other workers who find ground 
connexion necessary to success. 
Method of Direct Excitation (Slaby-Arco). 
In the method of directly exciting 
Fig. 10. the oscillations, one point of the 
condenser circuit is joined to the 
antenna, another point to earth. 
A diagram of the connexions 
is shown in fig. 10§. A and B 
are the terminal binding- posts of 
the secondary of the induction-coil, 
the distance between them being 
22cms. The spark-knobs, K, K, were 
16°5 mms. in diameter, and the spark 
leneth was from 1 to 2 mms. The 
leyden-jar had a mean diameter of 
5-7 cms., with walls about 4 mms. 
thick. The coatings were 10 cms. 
in height and of area about 180 square 
ems. The lengths of the various parts 
of the circuit are indicated on the figure, the entire condenser 
circuit having a length of approximately 
D3 +23 +22 + 23°5 + 16=137°5 cms. 
The wire CD wrapped about the jar was heavily insulated 
and consisted of 24 turns. This corresponds to Slaby’s 
“syntonizing coil,’ though, of course, it was not used for 
syntonization in my experiments. The turns were about 
2 cms. apart, so that its self-induction was practically the 
* K. Lecher, Phys. Zeitschrift, iii. p. 13 (1902) ; iv. p. 320 (1908). 
+ Heaviside, Electromagnetic Theory, vol. i. § 60; vol. ii. § 393. See 
preface to vol. ii. 
{ A. Kopsel, Dingler’s Polytechnisches Journal, June 1903; abstracted 
in N.Y. Electrical World and Engineer, Aug. 29, 1903. See also a letter 
by R. A. Fessenden on “Theories in Wireless Telegraphy” in N.Y. 
Electrical World and Engineer, Oct. 31, 1903. 
§ The arrangement was taken from that described by the Algemene 
Elektrizitdts Gesellschaft in their circular regarding the Slaby-Arco 
system, 1902. See also Boulanger et Ferrié, Télégraphie sans Fil, p. 156, 
Ath ed., 1902. 
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