372 POPULAR SCIENCE MONTHLY. 



in which the radiator draws off gradually a large supply of energy 

 from a non-radiating circuit, and so sends out a true train of waves, 

 and not mere impulses, into the ether, and as we shall see later on, it 

 is only when the radiation takes place in the form of true wave trains 

 that anything like syntony can he obtained. 



There are a number of variants of the above methods of arranging 

 the radiator and associated energy-storing in circuit. Descriptions of 

 these arrangements will be found in patents by Mr. Marconi, Professor 

 Slaby and Count von Arco, Sir Oliver Lodge, Dr. Muirhead, Professor 

 Popoff, Professor Fessenden and others. In all cases, however, they 

 are variations of the three simple forms of radiator already described. 



Eeturning to the analogy with the air or steam siren suggested at 

 the commencement of this article, the reader will see, in the light of 

 the explanations already given, that all parts of the air wave producing 

 apparatus have their analogues in the electrical radiator as used in 

 Hertzian wave telegraphy. The object in the one case is to produce 

 rapid oscillations of air particles in a tube, which result in the produc- 

 tion of an air wave in external space; in the other case, the arrange- 

 ment serves to produce oscillations of electrons or electrical particles 

 in a wire, the movements of which create a disturbance in the ether 

 called an electrical wave. Comparing together, item by item, it will 

 be seen, therefore, that the induction coil or transformer used in con- 

 nection with electric wave apparatus is analogous to the air pump in 

 the siren plant. In the electrical apparatus, this electron pump is 

 employed to put an electrical charge into a condenser; in the air wave 

 apparatus, the air pump is employed to charge an air vessel with high 

 pressure air. From the electrical condenser the charge is released 

 in the form of a series of electrical oscillations, and in the air wave 

 producing appliance, the compressed air is released in the form of 

 a series of intermittent puffs or blasts. In the electrical wave pro- 

 ducing apparatus, these electrical oscillations in the condenser circuit 

 are finally made to produce other oscillations in an air wire or open cir- 

 cuit, just as the puffs of air finally expend themselves in producing 

 aerial oscillations in the siren tube. Finally, in the one case we have 

 a series of air waves and in the other case, a series of electrical waves. 

 These trains of electric waves or air waves, as the case may be, are 

 intermitted into long and short groups, in accordance with the signals 

 of the Morse alphabet, and therefore tlio Hertzian wave transmitter, 

 in whatever form it may be employed, wlien operated by means of a 

 Marconi aerial, is in fact an electrical siren a])paratus, the function 

 of which is to create periodic disturbances in the universal ether of 

 the same character as those which the siren produces in atmospheric 

 air. 



{To be contintied.) 



