Theory of the- Striated Discharge. 1001 



hydrogen in agreement with those deduced from Goldstein's 

 expression. 



At very low pressures the thickness of the dark part of 

 the striation depends only upon ?', the intensity of the 

 current, varying as i~i, see equation (19). As the current 

 density in the narrow parts of the tube is greater than that 

 in the wide, the dark parts as well as the bright ones will be 

 thinner in the narrow tube than in the wide. As i varies 

 inversely as r 2 , the thickness of the dark parts will be pro- 

 portional to r ; it will therefore diminish more rapidly with 

 the radius of the tube than that of the bright parts, which 

 only varies as r*. Thus the narrower the tube the larger will 

 be the ratio of the bright places to the dark ones. 



From equations (9) and (16*) we see that the energy of 

 the electrons in a uniform column and the maximum energy 

 they acquire in a striated column increase with i the current 

 density : as this is greater in the narrow parts of the tube 

 than in the wider ones, the electrons will acquire greater 

 energy in the narrow parts. With very narrow tubes this 

 effect may be very considerable, so that the junction of a 

 narrow with a wide tube, the latter being the nearer to the 

 anode, may be regarded as a source of high-speed electrons 

 and thus produce effects in its neighbourhood analogous to 

 those produced by a cathode. 



The similarities between the effects observed at a con- 

 striction and those occurring near a cathode were pointed 

 out long ago by Goldstein. 



Summary. 



The distribution along- the line of discharge in a vacuum 

 tube of the energy of the electrons and the intensity of the 

 electric force is investigated when the current through 

 the gas is carried by the electrons. It is shown that when 

 the pressure is below a certain value depending on the 

 nature of the gas in the tube, there will be periodic varia- 

 tions in the energy of the electrons and the electric force, 

 and that these variations would produce periodic variations 

 in the luminosity such as are observed in the striated 

 discharge. 



Phil. Mag. S. 6. Vol. 42. No. 252. Dec. 1921. 1 U 



