for Production of Luminosity in Atmospheric Neon. 923 



tribnted in the same way about the nucleus in each case. 

 The existence of the three ionization velocities would be 

 expected if atmospheric neon consisted of three different 

 elements, and in this case it would be possible to excite 

 the spectrum of each element in turn by gradually in- 

 creasing the speed of the stream of electrons bombarding 

 the gas atoms. It was with the view of obtaining some 

 further information about the three ionizing velocities tliat 

 the experiments described in the present paper were under- 

 taken. Some preliminary experiments, referred to in our 

 earlier paper, had shown that in order to obtain conclusive 

 evidence it would be necessary to use some arrangement 

 for concentrating the rather feeble glow which appeared 

 in the gas at certain velocities of the electron stream. This 

 concentration of the luminosity was obtained by using a 

 stronger magnetic field in the manner described below. 



Description of Apparatus *. 



The source of electrons was a platinum filament F (fig. 1) 

 covered with a thin coating of lime. This was about 8 mm. 



* I wish to acknowledge my indebtedness to the Government Grant 



Committee of the Royal Society for the means o( purchasing some of 

 the apparatus and materials used in this research. — F. II. 



