Signalling through space without wires : being a description of the work of Hertz & his successors . Fig. 11.—A Small Dumb-bell Form of Radiator for Impulsive Rush. Many of these senders will do for receivers too, giving offsparks to other insulated bodies or to earth ; but besides theHertz type of receiver, many other detectors of radiation have. Fig. 12.—Dr. Lodges Hollow Cylindrical Radiator, arranged horizontallyagainst the outside of a Metal-lined Box containing the Spark-producingApparatus. Half natural size. Emitting 3in. waves. been employed. Vacuum tubes can be used, either directlyor
Signalling through space without wires : being a description of the work of Hertz & his successors . Fig. 11.—A Small Dumb-bell Form of Radiator for Impulsive Rush. Many of these senders will do for receivers too, giving offsparks to other insulated bodies or to earth ; but besides theHertz type of receiver, many other detectors of radiation have. Fig. 12.—Dr. Lodges Hollow Cylindrical Radiator, arranged horizontallyagainst the outside of a Metal-lined Box containing the Spark-producingApparatus. Half natural size. Emitting 3in. waves. been employed. Vacuum tubes can be used, either directlyor on the trigger principle, as by Zehnder (Fig. 13),f theresonator spark precipitating a discharge from some auxiliary * J. J. Thomson, Recent Researches, 344. f Wied. Ann., XLVII., p. 77. WORK OF HERTZ LECTURE. 15 battery or source of energy, and so making a feeble disturb-ance very visible. Explosives may be used for the samepurpose, either in the form of mixed water-gases or in theform of an Abels fuse. FitzGerald found that a tremendouslysensitive galvanometer could indicate that a feeble s-park hadpassed, by reason of the consequent disturbance of electricalequilibrium which settled down again through the galvano-meter.* This was the method he used in this theatre fouryears ago. Blyth used a one sided electrometer, and has
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