i6o 



THE POPULAR SCIENCE MONTHLY. 



ence waving about like a flexible wand as I move tbe magnet to 

 and fro. 



This action of the magnet is very curious, and if carefully fol- 

 lowed up will elucidate other properties of radiant matter. Here 



(Fig. 15) is an exactly similar tube, but having at one end a small 

 potash tube, which if heated will slightly injure the vacuum. I turn 

 on the induction-current, and you see the ray of radiant matter 

 tracing its trajectory in a curved line along the screen, under the in- 

 fluence of the horseshoe magnet beneath. Observe the shape of the 

 curve. The molecules shot from the negative pole may be likened to 



a discharge of iron bullets from a mitrailleuse, and the magnet be- 

 neath will represent the earth curving the trajectory of the shot by 

 gravitation. Here on this luminous screen you see the curved trajec- 

 tory of the shot accurately traced. Now suppose the deflecting force 

 to remain constant, the curve traced by the projectile varies with the 

 velocity. If I put more powder in the gun, the velocity will be greater 

 and the trajectory flatter ; and if I interpose a denser resisting medium 

 between the gun and the target, I diminish the velocity of the shot, 

 and thereby cause it to move in a greater curve and come to the 

 ground sooner. I can not well increase before you the velocity of 

 my stream of radiant molecules by putting more powder in my bat- 

 tery, but I will try and make them suffer greater resistance in their 



