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



But such charges are not acquired during formation, for in the 

 absence of the rays the motion of the particles is not influenced 

 by the electric field, and particles are equally affected when the 

 rays are turned on, whether they were formed before or after the 

 rays are allowed to act. 



Any charges acquired from the ions produced in the gas do 

 not give rise to the observed motions, for if both kinds of charges 

 are present, the streams should separate into two parts, one going 

 to each plate; and if on the other hand near each plate the 

 particles get a charge opposite to that of the plate we could not 

 thereby explain an experiment to be described later where both of 

 the streams are drawn to the same plate. 



While it thus seems clear that the motion of the stream is 

 a fair representation of what is going on in the gas when the 

 particles are not present, still in order to test this point further 

 the following experiment was performed. 



A carbonic acid gas generator was connected to a glass tube 

 which ended in a small opening and projected upwards through 

 the bottom K of the box PP' in fig. 1. A narrow jet of carbonic 

 acid gas could thus be sent upwards in the neighbourhood of and 

 parallel to one of the plates. 



The jet was made visible due to its different refractive index, 

 by projecting the whole apparatus with an arc-light as a shadow 

 upon a screen. 



With some care in choosing the proper orifice of efflux it was 

 possible to obtain a portion of the jet, which maintained a distinct 

 form even though its upward velocity was not large compared to 

 the motions under investigation. 



When the rays were turned on while the plates were at a 

 different potential, the jet of carbonic acid gas was deflected 

 towards its neighbouring plate, the same effect as was obtained 

 by using the ammonium chloride particles. Since however a gas 

 molecule cannot become electrified, the result here obtained 

 cannot be ascribed to any secondary effect, and it is evident that 

 during conduction the gas itself is set into motion. 



It is well known that gas movements accompany the passage 

 of electricity through gases in some other cases, and they are 

 explained as due to the movement of electrified carriers through 

 the gas. 



In seeking to find the cause of the convection currents here 

 under consideration we are at once led to ascribe them to the 

 motion of the charged ions by means of which the conduction is 

 carried on. 



When an ion starts moving through a gas under the action of 

 an electromotive force, its resulting velocity is assumed to become 

 constant in a very short time. 



