154 



Mr. William CrooTces 



[April 4 



the magnetic deflection of the trajectory of the molecules is the same 

 as has been found to hold good at a lower vacuum. The former 

 experiment was with a very high vacuum. This is a tube with a low 

 vacuum (Fig. 15). On passing the induction spark it passes as a 



narrow line of violet light joining the two poles. Underneath I have 

 a powerful electro-magnet. I make contact with the magnet, and 

 the line of light dips in the centre towards the magnet. I reverse 

 the poles, and the line is driven up to the top of the tube. Notice 

 the difference between the two phenomena. Here the action is 

 temporary. The dip takes place under the magnetic influence; the 

 line of discharge then rises, and pursues its path to the positive pole. 

 In the high exhaustion, however, after the ray of light had dipped to 

 the magnet it did not recover itself, but continued its path in the 

 altered direction. 



Fig. 15. 



During these experiments another property of this molecular 

 discharge has made itself very evident, although I have not yet 

 drawn attention to it. The glass gets very warm where the green^ 

 phosphorescence is strongest. The molecular focus on the tube' 

 which we have just seen (Fig. 12) would be intensely hot, and I have 

 prepared an apparatus by which this heat at the focus can be in- 

 tensified and rendered visible to all present. This small tube (a) 



