190 



Commendatore G. Marconi 



[June 2, 



upon my syntonic system of 1900, to whicli have been added nume- 

 rous improvements. 



An important innovation from a practical point of view was the 

 adoption at Clifden and Glace Bay of air condensers, composed of 

 insulated metallic plates suspended in air at ordinary pressure. In 

 this manner we greatly reduce the loss of energy which would take 

 place in consequence of dielectric hysteresis were a glass or solid di- 

 electric employed. A very considerable economy in working also 

 results from the absence of dielectric breakages, for, should the 

 potential be so raised as to even produce a discharge from plate to 



Fig. 4. 



plate across the condenser, this does not permanently affect the value 

 of the dielectric, as air is self-healing and one of the few commodities 

 which can be replaced at a minimum of cost. 



Various arrangements have been tried and tested for obtaining 

 continuous or very prolonged trains of waves, but it has been my ex- 

 perience that, when utilising the best receivers at present available, it 

 is neither economical nor efficient to attempt to make the waves too 

 continuous. Much better results are obtained when groups of waves 

 (Fig. 5) are emitted at regular inter\'als in such manner that their 

 cumulative effect produces a clear nuisical note in the receiver, which 

 is tuned not only to the periodicity of the electric waves transmitted, 

 but also to their group frequency. 



