MATTER, SPACE, AND TIME 231 



effect. This curious result indicates that the 

 ionizing action is independent of the state of 

 stability of the molecule, and prevents us from 

 finding in this way an explanation of the small 

 number of the ionized molecules in the path of 

 the rays. 



It is possible that some other rare condition, 

 unaffected by temperature, may be the necessary 

 preliminary to ionization by incident radiation ; 

 but it is also possible that the explanation of the 

 smallness of the ionization is to be sought in the 

 idea that the advancing wave is discontinuous, 

 and is composed of a number of parallel tremors 

 running along discrete tubes of force. The tubes 

 of force being scattered at wide intervals through 

 space, comparatively few molecules would lie in 

 their paths, and only a few would be affected by 

 waves running along the tubes. Matter has been 

 analysed into discrete particles ; electricity has 

 been shown to be made up of indivisible units ; 

 and now it seems possible that light in physical 

 reality, as well as in text-books of optics, is 

 composed of a number of separate rays. Perhaps 

 there is no need to invent a continuous sether — 

 a system of Faraday tubes radiating from electrons 

 may suffice. 



Moreover, serious difficulties have arisen in 

 the interpretation of the facts of radiation. To 

 meet these difficulties we have been forced to 

 regard radiation as emitted not continuously but 

 in discrete units or quanta, just as matter is not 

 continuous but atomic. 



In this quantum theory, Thomson finds a place 

 for Faraday's tubes. He regards the electrons in 

 his model of the atom, described on page 216, as 



