1902.] 



on the Progress of Electric Space Telegraphy. 



199 



which is known to be a persistent oscillator, to set up the required 

 number of oscillations in the radiator. An arrangement consisting 

 of a circuit containing a condenser and a spark-gap constitutes a very- 

 persistent oscillator. Prof. Lodge has shown us how, by placing it 

 near another similar circuit it is possible to demonstrate interesting 

 effects of resonance by the experiment usually referred to as that of 

 Lodge's syntonic jars. But, as Lodge points out, " a closed circuit 

 such as this is a feeble radiator and a feeble absorber, so that it is not 

 adapted for action at a distance." I very much doubt if it would be 

 possible to affect an ordinary receiver at even a few hundred yards. 

 It is, however, interesting to notice how easy it is to cause the energy 

 contained in the circuit of this arrangement to radiate into space. 

 It is sufficient to place near one of its sides a straight metal rod or 

 good electrical radiator, the only other condition necessary for long- 

 distance transmission being that the period of oscillation of the wire 

 or rod should be equal to that of the nearly closed circuit. Stronger 

 effects of radiation are obtained if the radiating conductor is partly 

 bent round the circuit containing the condenser (so as to resemble 

 the circuits of a transformer). 



My first trials with this system were not successful, in consequence 

 of the fact that I had not recognised the necessity of attempting to 

 tune to the same period of electri- 

 cal oscillations (or octaves) the two 

 electrical circuits of the transmit- 

 ting arrangement (these circuits 

 being the circuit consisting of the 

 condenser and primary of the trans- 

 former and the aerial or radiating 

 conductor and secondary of the 

 transformer). Unless this condition 

 is fulfilled, the different periods of 

 the two conductors create oscilla- 

 tions of a different frequency and 

 phase in each circuit, with the 

 result that the effects obtained are 

 feeble and unsatisfactory on a tuned 

 receiver. The syntonised trans- 

 mitter is shown in Fig. 1. The 

 period of oscillation of the vertical 

 conductor A can be increased by 

 introducing turns of wire, or de- 

 creased by diminishing their num- 

 ber, or by introducing a condenser 

 in series with it. The condenser 



in the primary circuit is constructed in such a manner as to render 

 it possible to vary its electrical capacity. 



The receiving station arrangements are shown in Fig. 2. Here we 

 have a vertical conductor connected to earth through the primary of 



Fig. 1. 



