XI. Ionisation by Röntgen Rays.
XII. Becquerel Rays.
XIII. Spark Discharge.
XIV. The Electric Arc.
XV. Discharge through Gases at Low Pressures.
XVI. Theory of the Discharge through Vacuum Tubes.
XVII. Cathode Rays.
XVIII. Röntgen Rays.
XIX. Properties of Moving Electrified Bodies.
Supplementary Notes.