RADTOTELEGRAPHY MARCONI. 



123 



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

 exception of the small motor revolving the disk. 



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

 volts when that of the battery or generators is 12,000. This poten- 

 tial is obtained in consequence of the rise of potential at the con- 

 denser plates, brought about by the rush of current through the 

 choking or inductance coils at each charge. These coils are placed 

 between the battery or generator and the condenser c, figure 6. 



No practical difficulty has been encountered either at Clifden or 

 Glace Bay in regard to the insulation and maintenance of these high- 

 tension storage batteries. Satisfactory insulation has been obtained 

 by dividing the battery into small sets of cells placed on separate 

 stands. These stands are suspended on insulators attached to girders 

 fixed in the ceiling of the batteiy room. A system of switches, 

 which can all be operated electrically and simultaneously, divides the 

 battery into sections, the potential of each section being low enough 

 to enable the cells to be handled without inconvenience or risk. 



The arrangement of aerial adopted at Clifden and Glace Bay is 

 shown in figure 7. This system, which is based on the result of tests 

 which I first de- 

 scribed before the 

 Koyal Society in 

 June, 1906, 1 not 

 only makes it pos- 

 sible to efficiently 

 radiate and receive 

 waves of any desired length, but it also tends to confine the main 

 portion of the radiation to any desired direction. The limitation of 

 transmission to one direction is not very sharply defined, but 

 nevertheless the results obtained are exceedingly useful for practical 

 working. 



In a similar manner, by means of these horizontal wires, it is 

 possible to define the bearing or direction of a sending station, and 

 also limit the receptivity of the receiver to waves arriving from a 

 given direction. 



The commercial working of radiotelegraphy and the widespread 

 application of the system on shore and afloat in nearly all parts of 

 the world has greatly facilitated the marshaling of facts and the 

 observation of effects. Many of these, as I have already stated, still 

 await a satisfactory explanation. 



A curious result which I first noticed over nine years ago in long- 

 distance tests carried out on the steamship Philadelphia, and which 

 still remains an important feature in long-distance space telegraphy, 



1 "On methods whereby the radiation of electric waves may be mainly confined, etc." Proc. Roy. 

 Soc., A, vol. 77, p. 413. 



Fig. 7. 



