[Fig. 22.—An amateur aerial (flat top).]

[Fig. 23.—Diagram showing the difference between loop and straightaway aerials.]

[Fig. 24.—Showing how wires are arranged and insulated.]

[Fig. 25.—Aerial insulator.]

[Fig. 26.—Leading-in insulator.]

[Fig. 27.–A side view of the aerial shown in Fig. 22.]

[Fig. 28.—Diagram showing how batteries may be arranged.]

[Fig. 29.—The power plant of a Marconi transatlantic station.]

[Fig. 30.—If a magnet be suddenly plunged into a hollow coil of wire a momentary current will be induced in the coil.]

[Fig. 31.—Magnetic phantom formed by a bar magnet.]