SIGNALING THROUGH SPACE WITHOUT WIRES. 



253 



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or thickness of sea water. The energy is absorbed in forming eddy 

 currents. There is no difficulty whatever in signaling through 15 

 fathoms. Speech by telephone has been maintained through 6 

 fathoms. Although this experiment has failed through water, it is 

 thoroughly practical through air to considerable distances where it is 

 possible to erect wires of similar length to the distance to be crossed on 

 each side of the channel. It is not always possible, however, to do 

 this, nor to get the requisite height to secure the best effect. It is 

 impossible on a lightship and on rock light-houses. There are many 

 small islands — Sark, for example — where it can not be done. 



In July last Mr. Marconi brought to England a new plan. My plan 

 is based entirely on utilizing electromagnetic waves of very low fre- 

 quency. It depends essentially on the 

 rise and fall of currents in the primary 

 wire. Mr. Marconi utilizes electric or 

 Hertzian waves of very high frequency, 

 and they depend upon the rise and fall 

 of electric force in a sphere or spheres. 

 He has invented a new relay which, for 

 sensitiveness and delicacy, exceeds all 

 known electric apparatus. 



The peculiarity of Mr. Marconi's 

 system is that, apart from the ordinary 

 connecting wires of the apparatus, con- 

 ductors of very moderate length only 

 are needed, and even these can be dis 

 pensed with if reflectors are used. 



The transmitter. — His transmitter is 

 Professor Righi's form of Hertz's radi 

 ator (fig. 2). 



Two spheres of solid brass, 4 inches 

 in diameter (A and B), are fixed in an 

 oil-tight case I) of insulating material, 

 so that a hemisphere of each is exposed, 

 the other hemisphere being immersed 

 in a bath of vaseline oil. The use of oil has several advantages. It 

 maintains the surfaces of the spheres electrically clean, avoiding the 

 frequent polishing required by Hertz's exposed balls. It impresses on 

 the waves excited by these spheres a uniform and constant form. It 

 tends to reduce the wave lengths — Righi's waves are measured in cen- 

 timeters, while Hertz's were measured in meters. For these reasons the 

 distance at which effects are produced is increased. Mr. Marconi uses 

 generally waves of about 120 centimeters long. Two small spheres, a 

 and b, are fixed close to the large spheres, and connected each to one 

 end of the secondary circuit of the "induction coii"C, the primary cir- 

 cuit of which is excited by a battery E, thrown in and out of circuit by 



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Fig. 2. 



-Diagram of the Marconi 

 apparatus. 



