ELECTRIC WAVE TELEGRAPH Y—FLEMING. 185 
to separate out the two constituent currents of an electrical oscilla- 
tion, and make them detectable by an ordinary galvanometer or 
telephone. I have also tried with some success a flame in which two 
platinum wires are immersed, one of which carries a bead of potas- 
sium sulphate as a means of rectifying oscillations of high frequency. 
It is well known that negative ions are then berated in the flame, 
and negative electricity can pass over more freely from the electrode 
which carries the bead of salt to the other than in the opposite direc- 
tion. I have not, however, found anything as simple and useful as 
the above-described low-voltage carbon filament glow lamp. More- 
over, other inventors have indorsed its utility by granting it the 
comphment of imitation. In October, 1906, Doctor de Forest 
described to the American Institute of Electrical Engineers an 
appliance he called an “ audion,” which is merely a replica of my 
oscillation valve, described to the Royal Society eighteen months 
previously and to the Physical Society of London six months before, 
particularly with reference to its use as a wireless telegraph receiver. 
Apart from the name the only difference introduced by him was to 
substitute a telephone and battery in series connected between the 
middle plate and positive terminal of the filament, for the gal- 
vanometer used by me connected between the middle plate and the 
negative terminal. As Mr. Marconi had before that time used my 
oscillation valve with a telephone with it for long distance work, 
and M. Tissot has found a galvanometer, used as I described it, 
effective up to 50 kilometers, the modification made by Doctor de 
Forest does not make any fundamental difference in the operation of 
the device as a wave detector.* 
Very closely connected with the question of the production of con- 
tinuous or undamped electric waves is that of the electrical trans- 
mission of speech through space without wires; in other words, 
wireless telephony. Some considerable progress has already been 
made in this direction. Any complete treatment would require a 
lecture in itself. If, however, we pass by the investigations of Bell 
with the photophone, Simon, Ruhmer, and others with apparatus 
employing the resistance variation of selenium by projected beams of 
powerful light, and also those of Preece, Gavey, and others with 
electro-magnetic induction, we may say that at the present time the 
chief interest attaches to methods of wireless telephony which involve 
the use of undamped electric waves. The problem may then be 
stated to be as follows: Articulate speech made against a diaphragm 
at a transmitting station has to affect similarly the diaphragm of a 
telephone at a receiving station not connected with it by wire. 
“Tn a private letter M. C. Tissot has already acknowledged gracefully my 
priority of invention in this matter, although he himself was independently 
working in the same direction. 
