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CONTENTS Chapter IV. THE OSCILLATION CONDENSER Function of the Condenser. What It Is. The Glass Plate Variety. Considerations of Weight, Capacity, and Space Occupied. A Simple Method of Determining Capacity. Forming a Standard Unit. Condensers for Portable Coils. The Use of Mica and Micanite. Relative Costs. The Murdock Moulded Condenser. Capacities, Sizes and Weights. The Oil-Immersed, Glass Plate Condenser for Permanent Installation. Chapter V. THE SPARK GAP The Simple Open Gap. Addition of Cooling Flanges. Use of Air Blast. The Rotary Spark Gap. Various Types and Advantages of Each. Number of Studs or Points Required. Speed of Motor. Air Gap between Sparking Points. The Quenched Gap. Principles of Operation. Simple Types for Amateur Construction. Importance of Regulation. Characteristics of the Discharge when Quenched Gap is Used. The Rotary Quenched Gap. Production of a High-Pitched Musical Note on 60-Cycle Current. Advantages in Radio Telegraphy. Chapter VI. OSCILLATION TRANSFORMERS Various Types of Air-Insulated High Frequency Current Transformers. The Simple Oudin Coil. Various Shapes and Proportions for the Secondary. Cones, Cylinders, Cages, Spirals, and the Advantages of Each. Various Primary Types. Round Conductor, EdgewiseWound Copper Strip, Hollow Tubing, Flat Copper Ribbon, and Stranded Conductor. Coupling. The Tesla Type of Coil. How it Differs from the Oudin. Advantages to be Gained. Tesla Secondaries. Means of Mechanical Support. Tesla Primaries. Proportions and Ratio of Diameter to Length. Combined or Double Resonator Type. Coupling. Oil and Wax Insulation for High Frequency Coils. Advantages and Disadvantages. Advantages of Close Coupling Possible. Spirally Wound and Wax Impreg nated Coils for Portable Outfits. Large Oil Insulated Coils for Testing and Other Permanent Installations. 84 39 45