436 Mr. J. Henry on the Be/lexion by Magnetic 



The following table gives for each figure the pressure 

 of the gas in the discharge-tube in cms. of mercury, the 



Figures. 



Gas. 



Mean 

 current. 



Pressure 

 of gas. 



Potential- 

 difference. 



8, a 



8,6 



8, c 



9, a 



9,6 



9,c 



9, d 



10, a 



10,6 



10, c 



11, a 



11,6 



11, c 



Air 



CO, 



Air 



CO, 



80 



80 



80 



95 



91 



155 



152 



44 



80 



275 



35 



215 



420 



14 

 22 

 3-7 

 35 

 0-8 

 46 

 2-8 

 33 

 1-4 

 1-4 

 41 

 41 

 1-6 



1100 

 1150 

 1425 

 1250 



965 

 1490 

 1320 

 1225 

 1100 

 1120 

 1475 

 1495 



950 



mean current in the discharge in divisions of the galvano- 

 meter-scale — one division of the scale corresponding toa current 

 of j-gj^ob of an ampere, — and the mean potential-difference 

 between the electrodes in volts. 



From these figures we see that there is very little, if any, 

 change of deflexion with pressure so long as the current in 

 the discharge is kept constant, but that the deflexion increases 

 with the current whether the pressure of the gas is kept 

 constant or not ; the increase in the deflexion, as measured by 

 the increased curvature of the path of the discharge, is not, 

 however, proportional to the increase of the mean current in 

 the discharge. Figs. 8 and 9 also show that the deflexion 

 is independent of the potential- difference between the electrodes 

 of the discharge. 



The magnetic force deflecting the discharge in these expe- 

 riments was nearly one C.G.S. unit, and the frequency of 

 discharge was about 60 per sec. 



Tension in the Gas carrying a Discharge. 



The part played by the gas in modifying the deflexion of 

 the discharge through it could be readily explained by sup- 

 posing that the dissociated molecules or ions in the gas along 

 the line of discharge are polarized and held in line by a sort 

 of tension, this tension being different for different gases ; on 

 this assumption, the greater the tension in any gas the less 

 would be the deflexion. 



Assuming the path of the discharge to be held in position 

 in this manner, and to be deflected like an elastic string bv 

 a uniform force everywhere perpendicular to the element of 



