1907.] 0)1 Recent Contributions to Electric Wave Telegraphy. 693 



sponding or exactly syntonised receiver at the same or a greater 

 distance. This claim is based on the known fact that for certain 

 types of receiving circuit, the current created in them can be largely 

 increased by increasing the number of oscillations in the incident 

 train of waves, so that if oscillations or waves are undamped they can 

 make up for feebleness l)y their persistency. This, however, depends 

 essentially upon the nature of the receiving circuit, and is only true 

 within certain limits. 



When electric waves radiated from one antenna fall on another 

 syntonised or tuned secondary cii'cuit they set up oscillations in 

 the latter of the same period. It might be thought that if these 

 impinging waves are undamped, we should have an infinitely large 

 current produced in the secondary circuit. As a matter of fact we do 

 not. The electro-motive impulses from the sender only increase the 

 secondary current up to a certain point. The secondary circuit 

 necessarily possesses resistance and other sources of energy dissipation 

 which rapidly increase with the current induced in it. Moreover, 

 when the secondary circuit has an antenna attached, this itself 

 radiates part of the energy it absorbs. Hence it follows that beyond 

 a certain point the energy thrown on to the secondary circuit is no 

 longer utilised to increase the current in it, but only just suffices to 

 maintain it. The case is exactly analogous to that of a body being 

 warmed by radiant heat. A thermometer exposed to full sunshine 

 only rises to a certain height. 



A comparison between the damped and undamped radiation, to be 

 vahd, must be made as follows : Assume that we have two wireless 

 transmitting stations side by side, one sending out intermittent trains 

 of feebly damped oscillations, the other continuous trains of undamped 

 oscillations, and let them be so adjusted that the transmitters take the 

 same mean power to work them. Let the frequency of these damped 

 and undamped waves so radiated be the same. At a distance let 

 there be a suitable movable receiving station, say a ship, with receiver 

 tuned to the same frequency. Then the principal question at 

 issue is, whether the undamped waves can affect this receiver at a 

 greater distance than the damped waves of the same integral energy. 

 Otherwise, at the same distance can the undamped wave station affect 

 the receiver when usmg less power than the damped wave station. 

 Since, however, by assumption the undamped waves from one station 

 have the same integral energy as the damped waves from the other, 

 the latter will have a higher initial value in each train to compensate 

 for their decreased value and intermittent cessation. Hence we may 

 ask another question, viz., What will be their relative effect on receiving 

 stations in their neighbourhood not quite in tune with the emitted 

 waves ? Can we bring the undamped waves nearer into tune with 

 these outlander stations without disturbing the latter, than we can 

 in the case of the damped waves, and if so within what ratio of wave 

 length ? Claims have been made for a great superiority in this 



