446 Mr. J. Henry on the Deflexion by Magnetic 



discharge between the electrodes, sent by an induction-coil, 

 noted. The pressure of the mercury vapour in the bulb was 

 first raised as high as possible by heating, and then allowed 

 to fall by cooling the bulb, but in no case was the discharge 

 very much deflected. The discharge was bent upwards a little 

 by the vertical current of vapour. 



The experiment showed that the deflexion of the discharge 

 in mercury vapour was very much less than in air or carbonic 

 acid gas for low pressures, and seemed even less than in 

 hydrogen. 



Fig. 15. 



d 



Comparison of Theory ivith Experiment, 



Taking the gases — hydrogen, air, and carbonic acid gas — 

 with which careful experiments were made, we find the mag- 



