CHAPTER VIII 



RECENT ELECTRICAL DISCOVERIES AND APPLIANCES, 

 WIRELESS TELEGRAPHY, ETC. 



IT is said facts are now being discovered and 

 physical theories developed the ultimate result of 

 which may be the explanation of the mysterious 

 phenomena presented by the corona of the sun, 

 the tails of comets, the aurora, terrestrial magnet- 

 ism and its variations, nebulae and the zodiacal 

 light. First, these facts are being established in 

 connection with the pressure exerted by light which 

 was pointed out by Maxwell and deduced by him 

 from his electro-magnetic theory of light, which is, 

 that when a pencil of light impinges perpendicularly 

 on an opaque object, it produces a pressure on the 

 surface of that object. This pressure is determined 

 by the condition that if the object were set in mo- 

 tion with the velocity of light and the force against 

 it kept up, the power to keep up the pressure would 

 be equal to that carried by the ray of light. 



Second, that particles smaller than atoms, called 

 corpuscles or ions, are thrown off with high velocity 

 from the intensely heated bodies. The sun, they 

 claim, being siich a body, it follows that such ions 

 must be shot out from it. On this theory it is held 

 that the explanation of a comet's tail is simple. 

 The comet evaporates on the side next to the sun 

 and, there being no pressure to hinder its expansion, 



