1902.] Mr. G. Marconi on Electric Space Telegraphy. 195 



WEEKLY EVENING MEETING, 



Friday, June 13, 1902. 



His Grace the Duke of Northumberland, K.G. D.C.L. F.R.S., 

 President, in the Chair. 



G. Marconi, Esq., M. Inst. E.E. 

 The Progress of Electric Space Telegraphy. 



Wireless Telegraphy, or telegraphy through space without con- 

 necting wires, is a subject which at present is probably attracting more 

 world-wide attention than any other practical development of modern 

 electrical engineering. That it should be possible to actuate an in- 

 strument from a distance of hundreds or thousands of miles and oblige 

 it at will to reproduce audible or visible signals through the effects 

 of electrical oscillations transmitted to it without the aid of any con- 

 tinuous artificial conductor, strikes the minds of most people as beino- 

 an achievement both wonderful and mysterious. If we examine the 

 subject closely we may, however, come to the conclusion that, although 

 telegraphy through space is certainly wonderful, as are likewise all 

 natural and physical phenomena, yet it is certainly in no way more 

 wonderful than the transmission of telegrams along an ordinary tele- 

 graph wire. The light and heat waves of the sun and stars travel 

 to us through millions of miles of space, and sound also reaches our 

 ears without requiring any artificial conductor. It is not, therefore, 

 wonderful that man should have devised means by which he is 

 enabled to confine electricity conveying messages or power to a wire 

 and cause the effect which we call an electric current to follow all 

 the turns and convolutions which may exist in the wire. 



We find that the first systems of telegraphy used by mankind 

 were truly wireless. A bonfire built on a hill by a band of aboriginal 

 Indians conveyed a signal wirelessly by etheric waves — in this case 

 lignt waves — to Indians on another hill, perhaps miles distant. Even 

 to-day there are innumerable systems of what may truly be called 

 wireless telegraphy in practical use. A red light at a railway crossing 

 conveys a signal by waves through the ether to the eye of the engine 

 driver. The red light is the transmitter, the eye the receiver. 



The method of space telegraphy of which I intend speaking to- 

 night is founded on a comparatively new way of controlling and 

 detecting certain kinds of etheric waves, much slower in rate of 

 vibration than light waves, called Hertzian waves, after the scientist 

 who first demonstrated their existence. The mathematical and 



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