SCIENTIFIC PROBLEMS IN RADIOTELEGRAPHY 367 



Again, as observed by Mr. Marconi and his staff, there are 

 great differences in the facility with which these waves are 

 propagated in different directions, as in some cases they 

 are more easily sent in north and south directions than in 

 east and west. Lastly, we have the same influence exerted by 

 daylight on the stray or natural waves as on the message- 

 bearing waves. 



Under some conditions of the atmosphere, radiotelegraphic 

 apparatus intended for moderate distances will send or receive 

 over unusually great distances and these ■' freak transmissions," 

 as they are called, are more likely due to some abnormal state 

 of the atmosphere than of the earth. Hence these vagaries of 

 transmission can hardly be explained merely by a surface wave 

 or by any regular process of transmission of wave energy. 



It is clear that the unravelling of the knotty problems of 

 radiotelegraphy is bound up with a much more complete 

 insight into the structure of the earth's atmosphere. It is 

 indeed curious how, as progress takes place in science, blows 

 are continually struck at our complacent ignorance. Time was 

 when we all confidently thought the earth's atmosphere was 

 merely a mixture of oxygen and nitrogen with a dash of carbon 

 dioxide and some aqueous vapour; then suddenly we learnt that 

 it contains argon, neon, helium, zenon, krypton and perhaps 

 traces of several other gases. Radiotelegraphy is now teaching 

 us that it is of a still more complicated character and possesses 

 constituents which have the property of refracting, perhaps 

 reflecting and also absorbing, long electromagnetic waves in an 

 extraordinary manner. 



Many of the mathematicians who have attacked this problem 

 of the bending of long electric waves round the earth have 

 fallen back on the hypothesis that there must exist at a high 

 level of the atmosphere a layer of rarefied gases which are so 

 much ionised that they form a very good conductor of electricity, 

 possibly as good as dilute sulphuric acid at its maximum con- 

 ductivity. This layer is assumed to have the property of 

 producing, by an inverted mirage effect, a reflection of long 

 electric waves. The hypothesis of long-distance transmission 

 that is then suggested is something as follows : When a radio- 

 telegraphic station is at work, the waves sent out horizontally 

 are diffracted to a small extent and may reach the receiving 

 stations at a very few hundred miles' distance directly. In 

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