as Radiators in Wireless Telegraphy. 6$3 



combined with the use of a suitable oscillation detector. 

 With this end in view, a closed primary-circuit had created 

 in it continuous or undamped electric oscillations, and its 

 inductive and radiative effect upon a similar closed receiving 

 circuit was measured by means o£ the Oscillation Valve or 

 Glow- Lamp Detector first described by the Author in 1904. 



It consists of a 12-volt carbon filament glow-lamp with a 

 metal cylinder surrounding the filament sealed into the bulb. 

 The cylinder is carried on a platinum wire sealed through 

 the glass. The filament is incandesced by a 6-cell secondary 

 battery. If the terminals o£ a condenser inserted in an 

 oscillatory circuit are connected, one to the cylinder and one 

 to the negative terminal of the lamp filament, and if an 

 ordinary movable coil galvanometer is inserted in this 

 circuit, then when oscillations occur in the condenser the 

 glow-lamp acts as an electrical valve and the galvanometer 

 is traversed by a continuous current which bears a definite 

 relation to the potential difference of the condenser terminals 

 and therefore to the current into it*. 



To calibrate the valve the following arrangement was 

 employed. An oscillatory circuit was arranged consisting 

 of one of the small square coils L (see fig. 1) and a condenser 

 or Leyden jar C in series with it. In this circuit at one point 

 was inserted a fine constantan wire having a thermo-junction 

 (T) of iron and bismuth or bismuth and tellurium in contact 

 with it. The arrangement actually employed was either the 

 thermo-junction used with the Author's Cymometers or else 

 the thermoelectric receiver described some time agoj (see 



% i). 



The galvanometer A associated with the junction was a 

 o-ohm single-pivot Paul galvanometer. The arrangement 

 •was calibrated by first passing measured continuous currents 



* This glow-lamp detector or oscillation valve was first described by 

 me in a British Patent Specification, No. 24,850 of 1904, and in 

 a Paper to the Royal Society (see Proc. Ptoy. Soc, vol. lxxiv. p. 476) 

 in February 1905. Also in a United States Patent Specification, 

 No. 803,684 of 1905, and in a Paper to the Physical Society of London 

 (see Phil. Mag. May 1906), as well as in a book on the 'Principles of 

 Electric Wave Telegraphy, pubished in May 1906. These publications 

 apparently failed to make it known in the United States, for in October 

 1906 Dr. Lee de Forest described to the American Institute of Electrical 

 Engineers precisely the same device, viz., a carbon filament glow-lamp 

 having a plate sealed into the bulb as a detector for electric oscillations, 

 as his own invention and re-christened this two-year old appliance an 

 audion. Xo re-christening, however, affects the fact that the appliance 

 had been in use by me long previously and especially described as a 

 receiver for wireless telegraphy. 



f See "Radiation from Bent Antennae.*' bv J. A. Fleming, Phil. Mas - . 

 December 1906, p. 592. 



