the Transmitting Antenna in Wireless Velegraphy. 131 
system. The former used a wire about 10 metres long, and 
explored it with a spark micrometer in which a blunt metal 
cone was opposed to a flat face of are carbon. According 
to the curve he obtained (fig. 1 of his article), there was a 
standing wave, with potential loops at the ends and a relative 
node in the middle. In my experiments there is a node at 
the end of the wire attached to the coil. Slaby concluded 
that the overtones present were very trifling and that the 
oscillation emitted was almost a pure fundamental. The 
fundamental is certainly present in great intensity, but 
the readings giving it are sometimes scattering, as mentioned 
above, and the curve is not very smooth. In some cases, 
too, as already seen, overtones show in considerable strength. 
Slaby also found that when the pole of the induction-coil 
was Joined, not to an end of the antenna, but to some other 
point, the oscillation produced showed considerable distortion. 
This effect is similar to that noted above in the case of the 
1000 ems. earthed wire. 
Braun used a wire 15 metres long stretched horizontally, 
and from it suspended five small Geissler tubes, each with a 
wire 50 cms. long hanging below it. When the coil was in 
action the tubes lighted up, but there was no trace of a node 
or a ventral segment. 
Inductive Method of Excitation (Braun, Marconi). 
The experimental disposition used for inductively exciting 
the oscillations about the antenna is illustrated in fig. 4. 
C,, C, are two condensers. From the 
inner coatings conductors lead off and end 
in knobs, between which sparks are made to 
pass by an induction-coil. The outer coatings 
are joined by a thick wire bent into a single 
turn which acts as the primary of a trans- 
former. The secondary of this transformer 
(AB) consists of afewturns. To one end of it 
(A) the antenna is joined, and to the other 
end (B) the earth, any desired capacity, or a 
wire similar to the antenna. 
The apparatus actually used in the investi- 
gation was the transmitter of the experimental 
set supplied by the Gesellschaft fiir drahtlose 
Telegraphie, Berlin, Germany, of the system 
Prof. Braun and Siemens & Halske. Each 
condenser consisted of four small tubular jars, 
17°5 mms. in diam., 2 mms. thick, and with coatings approxi- 
mately 7°5 ems. high. The spark-gap was from 1 to 2 mms. 
Fig. 4. 

