RADIOTELEGRAPH Y—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 ¢, 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 battery 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 
Royal 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, 
Fig. 7. 
1**On methods whereby the radiation of electric waves may be mainly confined, etc.’? Proc. Roy. 
Svc., A, vol. 77, p. 413. 
