170 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1909. 
method, or the method of quenched sparks, which is based on the fact 
that if we can quench or stop the spark in the condenser circuit after 
the first few oscillations, the oscillations of the antenna then take 
place freely and with a single fre- 
quency (see fig. 114). 
The principle which underlies this 
method is the well-known fact, to 
which particular attention was called 
by Prof. M. Wien, of Danzig, in 1906, 
that the damping effect of very short 
sparks is extremely large. Hence, if 
we form a spark gap consisting of a 
large number of very small spark gaps in 
Fic. 11.—Method of utilizing waves series, say 10 gaps each of 0.3 mm., and 
of both frequencies emitted by E 
inductively coupled transmitting 1f we keep the spark surfaces cool, 
TEMES SUEY then not only can no are form be- 
“tween these surfaces but the condenser spark is immediately 
quenched. Moreover, if we supply this spark gap, either from a high 
frequency alternator, or from a low resistance transformer, we can 
produce as many as 2,000 sparks per second. A form of discharger 
for this purpose has been devised in Germany which consists of a 
series of copper disks or 
copper boxes cooled with 
water, the flat surfaces of 
which are placed in con- 
tiguity, but separated by 
very thin rings of mica. 
The interspace between 
the boxes 1s not mere 
than one one-hundred- 
and-twenty-fifth of an 
inch, and ten or twelve 
of these disks or boxes 
are placed in series (see 
fig. 11s). The row of 
boxes takes the place of 
the ordinary spark balls, 
and is connected to the 
secondary terminals of a 
transformer, fed by a high 
frequency alternator, and also connected to an oscillatory circuit. 
When the transformer is in action it produces a very large number, 
1,000 or more, of oscillatory discharges of the condenser per second, 
each of which has a large initial amplitude, but quickly dies out. The 
inductively or directly coupled antenna hence receives a very large 
Ordinary Spark 
Primary 
Secondary |\ 
Primary 
Fic. 114. Oscillations in inductively coupled circuits. 
