Section titles are ...(1) Introduction ...(2) Arc in Air Between Carbon Electrodes ...(3) Arc in Air Between Other Substances than Carbon ...(4) Arc with Pressures Greater or Less than Atmospheric Pressure and in Other Gases than Air ...(5) Mercury Arc ...(6) Alternating Current Arc ...(7) Photometry of the Electric Arc ...(8) Use of Arc in Wireless Telephony [including Whispering Arc and Whistling Arc] ...(9) Theory of the Electric Arc ...(10) Ionization at Cathode of Arc. The following is a selection of some of the individual chapters from witihin these sections ... Relation Between Potential Difference, Current and Length of Arc ... E.M.F. Required as Distinct from Voltage of Arc ... "Negative Resistance" ... Residual E.M.F. ... Effect Produced by Cooling Electrodes ... Size of Anode Crater ... Enclosed Arc ... Flaming Arc ... Arc Between Metals ... Arc Between Oxides ... Magnetite Arc ... Arc Between Electrolytes ... Arc Between Unlike Electrodes ... Carbon Arc in a Vacuum ... Metal Arc in a Vacuum ... Electric Force Through Arc ... Arc in Quartz Tubes ... Modification of Arc to Produce White Light ... Fall of Potential in AC Arc ... Mercury Arc Rectifier ... Comparison of Diffrerent Kinds of Arcs ... Ionization by Impact ... Ionization by Hot Solids ... Ionization at Surface of the Anode ... Cause which Determines the Amount of the Cathode Drop ... Ionization of Gas Between Electrodes, etc.