(a) The Mechanical Effect. In the tube shown in Fig. 1 a light wheel is made to roll along the glass rails, either to the left or to the right, depending on whether A or B is made the cathode. The rotation of the wheel is caused by the stream of particles sent off by the cathode, which strike the vanes on the top of the wheel.
(b) The Heating Effect. The tube shown in Fig. 2 is a focus tube having a thin piece of platinum at the focus of the cup-shaped cathode. The continuous blows of the re- pelled particles constituting the cathode rays cause this piece of platinum to become red-hot.
(c) The Magnetic Effect. By using a straight tube and placing a strong electro- magnet near one side, as in Fig. 3, it is possible to deflect the rays from their straight path whenever an electric current is sent through the coil of the electromagnet. The fact that the rays are deflected by a magnetic field proves that they are made up of charged bodies, and the direction of this deflection indicates the kind of charge carried.
(d) The Fluorescent Effect. -The tube shown in Fig. 4 contains, as the anode, a cross of aluminum or mica, hinged to a support at the bottom. When a current is sent through the tube, the bombardment of the cathode rays causes the glass walls of the tube to glow with a fluorescent light except where they are protected by the cross, which
itself receives the bombardment. This shows the straight- line path of the particles. If now the cross is suddenly swung down on its hinge to the bottom of the tube, the part of the tube that was dark before will glow more brightly than the rest. This is due to the fact that the fluorescence fades out after the rays have been striking the glass for some time. The glass may be said to possess a fluorescent fatigue.
