1. ROYAL INSTITUTION LECTURE ON THE WORK OF HERTZ AND SOME OF HIS SUCCESSORS:-- PAGES Biographical Introduction 1 Elementary Explanation about Electrical Radiation and Absorption and the Effect of Syntony 3-8 Syntonic Leyden Jar Experiment 6, 21 Side Observations on the Effect of Light on Electric Discharge 9-12 Various Detectors of Radiation 13-23 Physiological Non-Effect of Sufficiently Rapid Alternations 17 Boltzmann Gap Detector--the Precursor of the Coherer 18 Branly’s Observations (_see also Appendix, page 95_) 20 Early Form of Coherer and of Branly Filings Tube 21-23 Early Signalling over 40 or 60 yards 24-25 Use of Telephone as Receiver 26 Experiments showing Syntony 27-28 Hypothesis concerning the Nature of Vision 29-31 Summary of Various Detectors of Radiation 30 Radiation Detected from extremely Weak Sparks, and by very compact Receiver with Collecting Wire 32-34 Vacuum Filings Tube 34 Effect of Metallic Enclosure 35-38 Experiments on Reflection, Refraction, and Polarisation of Radiation 39-42 Note about Electric Waves on Wires 43 2. APPLICATION OF HERTZ WAVES AND COHERER SIGNALLING TO TELEGRAPHY 45-48 Coherer Behaviour and Tommasina’s Experiment 49 Single-Point Coherer 55 General Remarks about Patent Law 50 Attempts at Syntonic Telegraphy 52-60 Syntonic Radiators and Receivers 51-56 3. DETAILS OF OTHER TELEGRAPHIC DEVELOPMENTS:-- Popoff’s 1895 Demonstration 60-62 Slaby’s Overland Experiments 63-66 Marconi’s Recent Demonstration 66-72 4. A HISTORY OF THE COHERER PRINCIPLE 73-87 Professor Hughes’ Early Observations before Hertz or Branly 88-94 Work of Monsieur Branly 95-108