. Robison's Manual of radio telegraphy and telephony for the use of naval electricians . ntial difference, and the con-denser continues to charge. At the next instant, however, the condenser MANUAL OF RADIO TELEGRAPHY AND TELEPHONY. 119 commences to discharge, increasing the direct arc current until it isentirely discharged; then the process repeats itself. Oscillations can be produced in this way from almost any form of arcand over a wide range of voltages, but it is found that high frequencyoscillations are best produced when the direct current voltage is high(500 volts or more), and when th
. Robison's Manual of radio telegraphy and telephony for the use of naval electricians . ntial difference, and the con-denser continues to charge. At the next instant, however, the condenser MANUAL OF RADIO TELEGRAPHY AND TELEPHONY. 119 commences to discharge, increasing the direct arc current until it isentirely discharged; then the process repeats itself. Oscillations can be produced in this way from almost any form of arcand over a wide range of voltages, but it is found that high frequencyoscillations are best produced when the direct current voltage is high(500 volts or more), and when the positive arc electrode is capable ofconducting away heat rapidly. Water is used as a cooling medium insteadof air, as with a spark transmitter, and to facilitate its application, thepositive (copper) electrode is made hollow. This rapid cooling of the arcplays a very important part in the production of the oscillations, as itcauses the arc to die down rapidly and increases the suddenness with whichthe current flows into the condenser. It has also been found that when the PILOT LAMP. Fig. 62.—Arc Arranged for Wireless Telephony. arc is formed in an atmosphere capable of assisting in this cooling, theenergy of the oscillations is vastly increased. The best gaseous conductorof heat is hydrogen, and consequently the best results are obtained in anatmosphere of hydrogen or some mixed gas or vapor containing illuminating gas gives excellent results, and recently alcoholand ether introduced into the arc chamber drop by drop and vaporizedby the heat of the arc has come into use. It has been suspected that thesegases and vapors may have some effect on the electrical conductivity ofthe arc as well as on its cooling, but this point is still unsettled. The energy of the oscillations which can be obtained from the arc ismcreased by forming it in a magnetic field the lines of force of which are atright angles to the arc length. The action of the magnetic field is twofold;
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