On Radiant Matter. 23 



I now put a magnet, #, over the tube, so as to deflect the 

 stream over or under the obstacle cd, and the result will be 



FIG. 17. 



rapid motion in one or the other direction, according to 

 the way the magnet is turned. I throw the image of 

 the apparatus on the screen. The spiral lines painted on 

 the wheel show which way it turns. I arrange the 

 magnet to draw the molecular stream so as to beat 

 against the upper vanes, and the wheel revolves rapidly 

 as if it were an over-shot water-wheel. I turn the 

 magnet so as to drive the Radiant Matter underneath ; the 

 wheel slackens speed, stops, and then begins to rotate the 

 other way, like an under-shot water-wheel. This can be 

 repeated as often as I reverse the position of the magnet. 



I have mentioned that the molecules of the Radiant 

 Matter discharged from the negative pole are negatively 

 electrified. It is probable that their velocity is owing to 

 the mutual repulsion between the similarly electrified pole 

 and the molecules. In less high vacua, such as you saw a 

 few minutes ago (Fig. 16), the discharge passes from one 

 pole to another, carrying an electric current, as if it were 

 a flexible wire. Now it is of great interest to ascertain if 

 the stream of Radiant Matter from the negative pole also 

 carries a current. Here (Fig. 18) is an apparatus which will 

 decide the question at once. The tube contains two negative 

 terminals (a, b) close together at one end, and one positive 

 terminal (c) at the other. This enables me to send two 

 streams of Radiant Matter side by side along the phos- 



