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ETHER WAVES AND THE MESSAGES THEY BRING 



of much greater wave length than any found in the solar spectrum. As the 

 temperature is increased the waves become shorter and shorter, until at about 

 525° C. the first red waves appear, and at from 800'^ to 1200° C. bodies have 

 reached a white heat. These infra-red waves — so called because of their posi- 

 tion in the spectrum — obey the same general laws as Hght waves. They are 

 refracted, reflected, and absorbed, and exhibit the phenomena of interference 

 and resonance. They travel with the speed of light. They have been made 

 the subject of special study by Rubens and von Baeyer of BerHn, and are 



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found to range in length from 8000 to 3,000,000 Angstrom units. This latter 

 length is equal to 0.03 cm. 



If an electric spark is passed between the terminals of an induction coil 

 or between the coatings of a Leyden jar, Hght, of course, is produced. The 

 effect of this light on the eye is that of a single flash of very short duration. 

 A suitable photographic apparatus shows, however, that what seems to be a 

 single flash of hght is in reaHty a succession of light pulses of very much shorter 

 duration, caused by the oscillation of the discharge between the knobs. These 

 oscillations set up in the surrounding ether waves very much Hke Hght waves, 

 but much longer than any we have thus far mentioned, ranging from about 0.3 

 cm. to thousands of meters in length. These are the waves used in wireless 

 telegraphy. Hertz first identified them as waves by shomng that they ex- 

 hibited the property of resonance. He also showed that they traveled with 

 the speed of Hght. From him they are known as Hertz waves. Since the 

 longest infra-red waves are 0.03 cm. long and the shortest of the Hertz waves are 

 about 0.3 cm. long, it follows that there is between the two a belt of unknown 

 waves if we assume that the spectrum is entirely continuous. 



As I have said, the Hertz waves are used in wireless telegraphy. An aerial 

 consisting usually of a large grid of wires is suspended high in the air. As a 

 train of these waves passes it, the aerial is engulfed in the alternate high and 

 low potentials which constitute the wave train. Therefore the aerial itself 

 alternates rapidly in potential. If the aerial be connected to the earth with 

 its constant potential, it is clear that an alternating current of high frequency 

 will exist in this connecting wire as the wave train passes. As the wave train 

 is produced in a spark-gap possibly hundreds of miles distant, it is clear that we 

 have here the foundation of a system of communication between the spark- 

 gap and the ground wire of the aerial. Some device for detecting and recording 



