602 



NATURE 



[June 29, 191 1 



by mean> of speci.-il direct-current generators ; these 

 niachinis i li.ir^i a storage battery consisting of 6000 cells 

 all connected 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 utilising the gassing voltage 

 of the storage cells. 



DISC DISCHARGER 



CONTNIUOUS CUKMNT 



Fig. 6. 



For a considerable portion of the day the storage 

 battery alone is employed, with a result that for sixteen 

 hours out of the twenty-four 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 volts when that of the battery or generators is 

 12,000. This potential is obtained in consequence of the 

 rise of potential at the condenser plates, brought about bv 

 the rush of current through the choking or inductance coil's 

 at each charge. These coils are placed between the batterv 

 or generator and the condenser c. Fig. 6. 



No pr;i(iiial difficulty has been encountered either at 

 Clifden 01 (.!;u.' Bay in regard to the insulation and 

 maintenance of these high-tension storage batteries. Satis- 

 factory 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 batterv-room. A system of 

 switches, which can all be operated electrically and 

 simultaneously, divides the batterv 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 

 Kay is shown in Fig. 7. This system, which is based on 

 the result of tests which I first described before the Roval 

 society in June, 1906,* not only makes it possible ' to 



^1 c" 9i"..H^*^°i'' whereby the Radiation of Electric Wav-s mav be mainly 

 contined, &c. Proceedings of the Royal Society, A. vol. Ixxvii., 1906. 



NO. 2174, VOL. 86] 



radiate efTiciently and receive waves of any desired length, 

 but it also tends to confine the main portion of the radia- 

 tion to any desired direction. The limitation of trans- 

 mission to one direction is not very sharply defined, but 

 nevertheless the results obtained are e.xceedingly useful for 

 practical working. 



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

 it is pos-sible to define the bearing or direction of a send- 

 ing station and also limit the receptivity of the receiver 

 to waves arriving from a given direction. 



The commercial working of radio-telegraphy and 

 the widespread application of the system on shore 

 and afloat in nearly all parts of the world have 

 greatly facilitated the marshalling 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 more than 

 nine years ago in long-di.stance tests carried out on 

 the ss. Philadelphia, and which still remains an 

 important feature in long-distance space telegraphy, 

 is the detrimental effect produced by daylight on the 

 propagation of electric waves over great distances. 



The generally accepted hypothesis of the cause of 

 this absorption of electric waves in sunlight is 

 founded on the belief that the absorption is due to 

 the ionisation of the gaseous molecules of the air 

 affected by the ultra-violet light, and as the ultra- 

 violet rays which emanate from the sun are largely 

 absorbed in the upper atmosphere of the earth, it is 

 probable that that portion of the earth's atmosphere 

 which is facing the sun will contain more ions or 

 electrons than that which is in darkness, and there- 

 fore, as Sir J. J. Thomson has shown,' this 

 illuminated or ionised air will absorb some of the 

 energy of the electric waves. 



The wave-length of the oscillations employed has 

 much to do with this interesting phenomenon, long 

 waves being subject to the effect of daylight to a 

 very much lesser degree than are short waves. 



Although certain physicists thought some years 

 ago that the daylight efTect should be more mark.^d 

 on long waves than on short, the reverse has been 

 my experience ; indeed, in some Transatlantic 

 experiments, in which waves about 8000 metres 

 long were used, the energy received by day at the 

 distant receiving station was usually greater than 

 that obtained at night. 



Recent observation, however, reveals the interest- 

 ing fact that the effects vary greatly with the direc- 

 tion in which transmission is taking place, the 

 results obtained when transmitting in a northerly 

 and southerly direction being often altogether 

 different from those observed in the easterly and westerly 

 one. 



Research in regard to the changes in the strength of 

 the received radiations which are employed for telegraphy 

 across the Atlantic has been recently greatly facilitated by 

 the use of sensitive galvanometers, by means of which th-^ 

 strength of the received signals can be measured with a 

 fair degree of accuracy. 



In regard to moderate power stations such as are 



employed on ships, and which, in compliance with the 

 International Convention, use wave-lengths of 300 and 

 600 metres, the distance over which communication can 

 be effected during daytime is generally about the same, 

 whatever the bearing of the ships to each other or to the 

 land stations, whilst at night interesting and apparently 

 curious results are obtained. Ships more than 1000 miles 

 away, off the south of Spain or round the coast of Italy, 



1 See Philosophical Magazine, Aueust, 1902, ser. 6, vol. iv., p. 253, J. J. 

 Thomson, " On some Consequences," &c. 



