1907-8.] Note on ■ Electrical Resistance of Spark Gaps. 
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XXII. — Note on the Electrical Resistance of Spark Gaps. By 
Robert A. Houstoun, Ph.D., D.Sc. Communicated by Professor 
A. Gray, F.R.S. 
(MS. received May 4, 1908. Read June 1, 1908.) 
Of recent years a considerable amount of work has been done in measuring 
the electrical resistance of spark gaps under different conditions. The 
subject is important, both for its application to wireless telegraphy and on 
account of its bearing on the mechanism of the spark gap. Spark spectra 
are, as is well known, more complex than arc spectra. Formerly this was 
attributed to a very high temperature in the spark, but it is now regarded 
as due to a disintegration of the atom produced in the spark gap. Or, as 
Baly puts it in his book on Spectroscopy, in the spark gap the atom is 
in a state of assisted radio-activity. If the current density in the spark 
gradually increases until it is strong enough to disintegrate a particular 
system in the atom, we should expect a new spectrum to be produced then,, 
and probably a change in the resistance of the spark gap. My experiments 
have shown me that our methods of measuring the resistance of spark gaps, 
are not nearly accurate enough to show such a change if it existed. 
The object of this note is to record the effect of changing the material 
of the electrode on the resistance of the spark gap for eight different 
metals, the other conditions being always the same. This has as yet been 
done only by Slaby’s method, in which an additional spark gap is inserted 
in the circuit. (Cf Fleming’s The Principles of Electric Wave Telegraphy , 
p. 184.) I employed the method of taking a resonance curve first used 
by Bjerknes, which according to Eickhoff * is much to be preferred to the 
former method. 
The apparatus consisted of an oscillator and a resonator (cf. fig.)- The 
oscillator consisted of a condenser K, the opposite sides of which were 
connected by short thick copper wires to the electrodes E, between which 
the spark passed. The electrodes, no matter what the metal was, were 
cylindrical, 4 mm. diameter, about 3 cms. long, and had rounded ends. 
They were connected to the secondary of a large induction coil. The 
condenser in the primary circuit was formed of six zinc plates 20 X 20 cms., 
placed at a distance of 2 cms. from one another, and hence had a capacity 
of 80 cms. The resonator was made in Drude’s form. It consisted of two 
VOL. XXVIII. 
* Wilh. Eickhoff, Phys. Zeits., Aug. 1, 1907, p. 494. 
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