ELECTRIC WAVE TELEGRAPH Y—FLEMING. 188 
brightly incandescent by a small battery. In this circuit a galvanom- 
eter and one circuit of a small transformer or induction coil was 
inserted. On connecting the other circuit of the transformer be- 
tween an antenna and the earth, I found that the oscillations set up 
in the antenna caused a deflection in the ordinary mirror-galvanom- 
eter. (See fig. 14.) The action is as follows: The antenna oscilla- 
tions induce others in the circuit of the transformer, which is in con- 
nection with the lamp. A movement of electricity in this circuit, which 
consists in the flow of negative electricity from the filament to the 
plate through the vacuum, can take place, since this negative electric- 
ity is, so to speak, carried across the vacuous space by the electrons 
emitted from the hot carbon. On the other hand, negative electricity 
can not flow in the opposite direction. Hence the glow lamp sepa- 
rates out the two oppositely directed movements of electricity and 
allows only one to pass. I therefore called the appliance an oscilla- 
tion valve. This instrument was shown by me to the Royal Society 
early in February, 1905, and was employed by Mr. Marconi soon after 
as a long-distance wireless-telegraph receiver,in conjunction with other 
improvements. M. Tissot, of the Naval College, Brest, in France, 
has made use of this glow-lamp detector, and with a sensitive galva- 
nometer has received signals at a distance of 50 kilometers. Employ- 
ing a special form of transformer, and a telephone in place of a gal- 
vanometer, Mr. Marconi has used it for some time past over distances 
of 200 miles or more, and finds it a very sensitive form of receiver. 
Since this particular form of electric wave detector was brought to 
notice by me, Doctor Wehnelt has found that a metallic wire, coated 
with oxides of calcium, barium, or other earthy metais, may be sub- 
stituted for the carbon filament in the vacuous bulb. 
The oscillation valve is capable of giving very remarkable effects 
when used as a receiver with a transmitter producing undamped 
waves. The reason for this is obvious. The valve passes all the 
unidirectional currents in the attached secondary circuit. If, then, 
these are intermittent damped trains, say having a frequency of 
100,000, and 50 trains of 20 oscillations per second, the total time 
during which electric current is passing is only one-thousandth of 
the whole time. Accordingly, if we, so to speak, fill up the gaps 
between the trains of oscillations with other oscillations, and generate 
a continuous train, we greatly increase the quantity of electricity 
passing and repassing any point in the secondary circuit, and the 
indications on a galvanometer in circuit with the valve are enor- 
mously increased. A true comparison between the two cases of 
@See The Electrician, Vol. LVIII, p. 730, Feb. 22, 1907. M. C. Tissot, “On 
Ionised Gas Electric Wave Detectors,” 
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