14 Mr Zeleny, On Convection Currents and on the [Oct. 31, 



divergence as the values given by Perrin for these gases are only 

 about one-tenth of those found above. 



The existence of the additive law for the ionization produced 

 by the rays indicates that this ionization is probably not the 

 separation of one atom from another in the molecule of a gas 

 but a process occurring in the atom itself. 



(6) On Convection Currents and on the Fall of Potential at 

 the Electrodes, in Conduction produced by Rontgen Rays. By 

 John Zeleny, B. Sc, Assistant Professor of Physics, University 

 of Minnesota. 



I. Convection Currents produced by Rontgen Rays. 



The passage of electricity through a gas under the influence of 

 Rontgen rays is accompanied by movements of the gas itself 

 which are of considerable magnitude. 



The presence of these convection currents can readily be made 

 visible by means of particles suspended in the gas, and for this 

 purpose it has been found convenient to use the ammonium 

 chloride particles formed by the action of ammonia and hydro- 

 chloric acid. 



One form of apparatus used for carrying on the experiments is 

 represented in elevation in fig. 1. 



Fig. l. 



The two brass plates A and B are each 6'3 centimetres high 

 and 2'8 centimetres wide, and act as electrodes in the gas, being 

 connected to the opposite poles of a battery of storage cells. 



The plates are enclosed in a box of which the sides P and P' 

 are formed of paraffin blocks, while the other two sides are glass 

 plates which leave the whole interior open to observation. 



