332 Dr. A. Schuster. Experiment* on the 



by Hittorf. I think a careful measurement of the radii of such 

 circles will give us important information, and I have already made 

 preliminary experiments which have shown me that such a measure- 

 ment is possible. 



The force exerted on each part of the current is proportional to 

 v X e, where v is the velocity of each particle, and e the amount of 

 electricity it carries. If the particle moves in a circle the force is also 



proportional to where r is the radius of the circle. Hence r must 

 T 



be proportional to v/e. 



Suppose, now, that the current is increased. This may mean either 

 that the number of particles carrying the discharge is increased, or 

 that the velocity of each particle is increased, or that the amount of 

 electricity is increased, or, finally, some combined effect of these three 

 causes. When we come to consider the positive part of the discharge, 

 I shall show that the number of particles taking part in the discharge 

 seems certainly increased by an increasing current, and this is also 

 evident from the mere appearance of the discharge ; this does not, 

 however, affect the influence of the magnet. I find as a result of 

 experiment that the diameter of the rings is considerably increased 

 by an increase in strength of the current ; hence an increased current 

 must either mean a larger velocity only, or, at any rate, a velocity 

 increasing in a quicker ratio than the amount of electricity carried. 

 Before going further we must consider in what way v depends on e. 

 Let the total fall of potential in the region in which the velocity is 

 acquired be F, than v will vary as the square root of Ye, and hence 



/F 

 the diameter of the ring will vary as A/ -. If e is constant the 



diameter of the ring ought to vary as the square root of the fall of 

 potential in the neighbourhood of the negative electrode. Here, then, 

 we have a definite experimental problem before us which I hope to 

 decide one way or another as soon as I have the necessary experi- 

 mental means at my disposal. At present I wish only to point out 

 that if e does vary there is every reason that it cannot vary otherwise 

 on the average than proportionally to F. Hence the diameter of the 

 ring ought to be independent of the current, which it is not. 



Experiments with Hittorf s Tube. 



Mr. Hittorf has described some phenomena which are, in my 

 opinion, particularly interesting, as putting beyond all reasonable 

 doubt the projection of particles away from the negative pole. 



The tube, or rather the bulb, which he used had two parallel 

 electrodes at a distance of only a few millimetres. It was found that 

 at very low pressures the discharge from the positive electrode took 



