Signalling through space without wires : being a description of the work of Hertz & his successors . t is when definite radiation is desired, it is well toput the radiator in a copper hat open in only one direction(Fig. 20), and in order to guard against reflected and collateralsurgings running along the wires which pass outside to theexciting coil and battery, as they are liable to do, I amaccustomed to put all the sending apparatus in a packing case WORK OF HERTZ LECTURE. 37 lined with tinfoil, to the outside of which the sending hat(Fig. 20) is fixed, and to pull the key of
Signalling through space without wires : being a description of the work of Hertz & his successors . t is when definite radiation is desired, it is well toput the radiator in a copper hat open in only one direction(Fig. 20), and in order to guard against reflected and collateralsurgings running along the wires which pass outside to theexciting coil and battery, as they are liable to do, I amaccustomed to put all the sending apparatus in a packing case WORK OF HERTZ LECTURE. 37 lined with tinfoil, to the outside of which the sending hat(Fig. 20) is fixed, and to pull the key of the primary excitingcircuit by a string from outside, so that not even key connec-tions shall protrude, else exact optical experiments areimpossible. Even then, with the lid of the hat well clamped on, some-thing gets out, but it is not enough to cause serious dis-turbance of qualitative results. The sender must evidently bethought of as emitting a momentary blaze of light whichescapes through every chink. Or, indeed, since the waves aresome inches long, the difficulty of keeping them out of an. Fiq. 21.—General arrangement of experiments with the Copper Hat,showing Metal Box on a Stool, standing outside the Theatre. The Box isnot exactly represented, but inside it the Radiators were fixed with agraduated series of apertures ; the Copper Hat containing the Cohereris seen on the Table with the Metal Box on the left of the Table containingBattery and Galvanometer Coil connected to it by a compo pipe conveyingthe wires, as in Fig. 19c ; the Lamp and Scale barely indicated at one sideof the Table ; a Paraffin Prism ; and a Polarising Grid of copper wiresstretched on a frame. [This figure is from a thumbnail sketch by P. Trotter, taken at the Lecture in 1894.] enclosure may be likened to the difficulty of excluding sound;though the difficulty is not quite so great as that, since areasonable thickness of metal is really opaque. I fancied 38 SIGNALLING WITHOUT WIRES. once or
Size: 2080px × 1201px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookidsi, booksubjectelectricity
