RECENT ADVANCES IK \VIEELESS TELEGRAPHY. 143 



The opinion has been expressed that the reason for shorter dis- 

 tances being covered by day is dne to the electrons propagated into 

 space by the sun, and that if these are continually falling like a 

 shower upon the earth, in accordance with the hypothesis of Professor 

 Arrhenius, then that portion of the earth's atmosphere which is facing 

 the sun will have in it more electrons than the part which is not facing 

 the sun, and therefore it may be less transparent to long Hertzian 

 waves. 



The full scientific explanation of this fact has not yet been given, 

 but Prof. J. J. Thomson has shoAvn in an interesting paper in the 

 Philosophical Magazine" that if electrons are distributed in a space 

 traversed by long electric waves, these will tend to move the electrons 

 in the direction of the wave, and Avill therefore absorb some of the 

 energy of the wave. Hence, as Professor Fleming has pointed out in 

 his Cantor lectures delivered at the Society of Arts, a medium through 

 which electrons or ions are distributed acts as a slightly turbid 

 medium to long electric waves. 



In fact, clear sunlight or blue skies, though very transparent to 

 light-waves, may act as a fog to Hertzian waves. Apparently the 

 amplitude of the electrical oscillations radiated has much to do with 

 the interesting phenomenon, for the author has found that if a con- 

 siderable amount of power is applied to the radiating apparatus of 

 the so-called short-distance stations, the difference between the range 

 of transmission by night and by day becomes at once apparent, 

 although no difference is made in the wave length radiated. 



A curious feature of what may be called the dajdight effect is the 

 suddenness with which it may cut off the signals at great distances. 

 These do not. as might be supposed, die off gradually as daylight 

 increases, but seem to fade away rapidl}^, and disappear entirely 

 within the space of about two minutes. 



The author does not for a moment think that this daylight effect 

 will prove to be a serious drawback to the practical application of 

 long-distance wireless telegraphy, as its result amounts to this, that 

 rather more power is required by day than by night to send signals 

 by means of electric waves over long distances. 



It has been stated that one of the serious objections to wireless 

 telegraphy lay in the fact that no means existed for directing the 

 energy emitted by the stations. If we assume this fact to be correct, 

 we certainly find that, if it presents certain disadvantages, it also 

 presents many perhaps counterbalancing advantages. For exam^Dle, 

 if a cable is laid between England and Canada it can only serve for 

 communication between these two countries: but if a wireless connec- 



o Vol. IV, Series G, August, 1902. 



