1011] 071 RadinteUgraphij. 1!»9 



are of such length as to just touch the side discs in passing, and 

 thereby bridge the gap between the hitter. 



With the freiiuency employed at Clifden, namely 45,000, when a 

 potential of 15,000 volts is used on the condenser, the spark ga]i is 

 practically closed during the time in which one complete oscillation 

 only is taking place, when the peripherical speed of the disc is about 

 600 feet a second. The result is that the primary circuit can con- 

 tinue oscillating without material loss by resistance in the spark gap. 

 Of course the number of oscillations which can take place is governed 

 by the breadth or thickness of the side discs, the primary circuit 

 being abruptly opened as soon as the studs attached to the middle 

 disc leave the side discs. 



This sudden opening of the primary circuit tends to immediately 

 quench any oscillations which may still persist in the condenser 

 circuit ; and this fact carries with it a further and not inconsiderable 

 advantage ; for, if the coupling of the condenser circuit to the aerial 

 is of a suitable v^alue, the energy of the primary will have practically 

 all passed to the aerial circuit during the period of time in which the 

 primary condenser circuit is closed by the stud filling the gap between 

 the side discs ; but, after this, the opening of the gap at the discs 

 prevents the energy returning to the condenser circuit from the aerial, 

 as would happen were the ordinary spark gap employed. In this 

 manner the usual reaction which would take place between the aerial 

 and the condenser circuit can be obviated, with the result that with 

 this type of discharger and with a suitable degree of coupling the 

 energy is radiated from the aerial in the form of a pure wave, the 

 loss from the spark gap resistance being reduced to a minimum. 



I am able to show a resonance curve taken at Clifden, which was 

 obtained from the oscillations in the primary alone (Fig. 5). 



An interesting feature of the Clifden plant, especially from a 

 practical and engineering point of view, is the regular employment 

 of high tension direct current for charging the condenser. Continuous 

 current at a potential which is capable of being raised to 20,000 volts 

 is obtained by means of special direct-current generators ; these 

 machines charge a storage battery consisting of 6000 cells all con- 

 nected in series, and it may be pointed out that this battery is the 

 largest of its kind in existence. The capacity of each cell is 40 

 ampere hours. When employing the cells alone the working voltage 

 is from 11,000 to 12,000 volts, and when both the direct-current 

 generators and the battery are used together the potential may be 

 raised to 15,000 volts through utilizing the gassing voltage of the 

 storage cells. 



For a considerable portion of the day the storage battery alone is 

 employed, with a result that for 16 hours out of the 2t no running 

 machinery need be used for operating the station, with the single 

 exception of the small motor revolving the disc. 



The potential to which the condenser is charged reaches 18,000 



