The subject-matter, as usual, is divided into chapters, but the sections are to be considered as subordinate chapters, having different shades of meaning, and the one not necessarily bearing a direct relation to the contents of its neighbor, but as, in a novel or a treatise on geometry, having its important part to play in conjunction with some later or preceding section. EDWARD P. THOMPSON. TEMPLE COURT BUILDING, NEW YORK, August, 1896. ------------------------------------------------------------------------ CONTENTS. ------- CHAPTER I. § 1. Secondary Current by Induction. No FARADAY Increased E. M. F. 2. Electric Spark and Increased E. M. F. PAGE by Induced Current. 3. Spark in Secondary Increased by FIZEAU Condenser in Primary. 4. Atmosphere around an Incandescent Live VINCINTINI Wire. 5. Magnetizing Radiations from an Electric HENRY Spark. 6. Arcing Metals at Low Voltage. FARADAY 7. Non-arcing Metals at High Voltage. WURTS Practical Application. 8. Duration of Spark Measured. WHEATSTONE 8_a_. Discharge—Intermittent, Constant, and FEDDERSEN Oscillatory—by Variation of Resistance. 9. Musical Note by Discharge with Small FARADAY Ball Electrodes. Invisible Discharge. 9_a_. Pitch of Sound Changed by Approach of FARADAY and Conductor Connected to Earth. MAYER 10. Brush Discharge. Color. Striæ. Nitrogen FARADAY Best Transmitter of a Spark, and its Practical Bearing in Atmospheric Lightning. Cathode Brushes in Different Gases. 11. Glow by Discharge. Glow Changed to FARADAY Spark. Motion of Air. Apparent Continuous Discharge during Glow. 12. Spark. Solids Perforated. LULLIN 13. Spark. Glass Perforated. Holes Close FAGE Together. Practical Application for Porous Glass. 14 and Spark. Penetrating Power. Conducting KNOCHENHAURER, 14_a_. Power of Gas. Relation of E. M. F. to BOLTZMANN, Pressure of Gases. Discharge through THOMSON Hydrogen Vacuum Continued with Less (KELVIN), Current than that Required to Start MAXWELL, it. VARLEY, HARRIS, and MASSON