vill TABLE OF CONTENTS 



CHAPTER PAGE 



V. MERCURY ARC 87 



Temperature 91 



Characteristic Curves 93 



Cathode Drop 96 



Anode Drop 97 



Electric Force Through Arc 97 



Arc in Quartz Tubes 100 



Velocity of Ions 101 



Modification of Arc to Produce White Light 102 



VI. ALTERNATING CURRENT ARC 105 



Between Carbons 105 



Characteristic Curves 106 



Current and Potential Difference at Different Phases 107 



"Dynamical" Characteristic Curves no 



Fall of Potential in A.C. Arc 112 



Phase Difference in Arc 113 



Arc Between Metals 114 



Arc Between Unlike Electrodes 118 



Arc in Other Gases than Air 119 



Mercury Arc Rectifier 120 



VII. PHOTOMETRY OF THE ELECTRIC ARC 126 



Distribution of Light 128 



Effect on Candle Power of Length of Arc, Current, Etc. . . . 130 



Intrinsic Brightness of Crater 132 



Flaming Arcs 132 



Metal, Including Mercury, Arcs 134 



Alternating-current Arcs 135 



Comparison of Different Kinds of Arcs 139 



Spectrum of Arc 142 



VIII. USE OF ARC IN WIRELESS TELEPHONY 146 



Whispering Arc 146 



Whistling Arc 148 



Application of Whistling Arc to Wireless Telephony 153 



IX. THEORY OF THE ELECTRIC ARC 156 



Definition of Ions and Electrons 156 



Causes Producing Ions 158 



lonization by Impact 158 



lonization by Hot Solids 159 



Fall of Potential Through Arc 160 



lonization at Surface of Cathode with Discharge at low 



Pressure 161 



lonization at Surface of Anode .. 162 



