............................................ Fig. 305.—Complete Thermopile. An Alcohol Lamp should be lighted and placed so that the Flame heats the Inside Ends of the Wires in the Center of the Wooden Ring. ........................................ Fig. 306.—A Reflectoscope. ........................................ Fig. 307.—How the Lens is Arranged and Mounted. ................... Fig. 308.—A View of the Reflectoscope from the Rear, showing the Door, etc. ........................................................ Fig. 309.—A View of the Reflectoscope with the Cover removed, showing the Arrangement of the Lamps, etc. ........................ Fig. 310.—A Socket for holding the Lamp. .......................... Fig. 311.—The Tin Reflector. ...................................... Fig 312.—Top View of Lamp Bank, showing how the Circuit is arranged. A and B are the Posts to which should be connected any Device it‘s desirable to operate. ............................................. Fig. 313.—A Glass Jar arranged to serve as an Electro-Plating Tank. Fig. 314.—A Rheostat. ............................................. Fig. 315.—A Pole-Changing Switch or Current Reverser. The Connecting Strip is pivoted so that the Handle will operate both the Levers, A and B. ............................................................ COMPLETE RECEIVING SET, CONSISTING OF DOUBLE SLIDER TUNING COIL, DETECTOR AND FIXED CONDENSER. ..................................... COMPLETE RECEIVING SET, CONSISTING OF A LOOSE COUPLER IN PLACE OF THE TUNING COIL, DETECTOR AND FIXED CONDENSER. .................... Fig. 316. A Complete Wireless Receiving Outfit. ................... Fig. 317.—Illustrating the Principle of the Tesla Coil. A Leyden Jar discharges through the Primary Coil and a High-Frequency Spark is produced at the Secondary. ........................................ Fig. 318.—Details of the Wooden Rings used as the Primary Heads. .. Fig. 319.—Details of the Cross Bars which support the Primary Winding. .......................................................... Fig. 320.—The Secondary Head. ..................................... A COMPLETE COHERER OUTFIT AS DESCRIBED ON PAGE 274. ............... THE TESLA HIGH FREQUENCY COIL. .................................... Fig. 321.—End View of the Complete Tesla Coil. .................... Fig. 322.—The Complete Tesla Coil. ................................ Fig 323.—Showing how a Glass-Plate Condenser is built up of Alternate Sheets of Tinfoil and Glass. ............................ Fig. 324.—A Diagram showing the Proper Method of Connecting a Tesla Coil. ............................................................. CHAPTER I MAGNETS AND MAGNETISM