Segnalazione attraverso lo spazio senza fili : descrizione del lavoro di Hertz e dei suoi successori . Wimshurst si fa sentire. Battendo il coperchio per ripristinare la resistenza, l'ago del galvanometro devia finché le scintille continuano a passare. Se, tuttavia, i fili sono spinti dentro in modo che proiettino soltanto una 106 SEGNALAZIONE SENZA FILI. Pochi millimetri, le scintille ancora che passano, alcuni rubinetti sono sufficienti per riportare l'ago a zero. Quando si tocca l'estremità del filo con le dita o un pezzo di conduttività metallica ripristinato immediatamente. I movimenti del galvanometerneedle erano re

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Signalling through space without wires : being a description of the work of Hertz & his successors . Wimshurst machine makes itself felt. Ontapping the lid to restore resistance the galvanometer needleremains deflected so long as the sparks continue to pass. If, however, the wires are pushed in so that they only project a 106 SIGNALLING WITHOUT WIRES. few millimetres, the sparks still passing, a few taps suffice tobring back the needle to zero. On touching the end of thewire with the fingers or a piece of metal conductivity isimmediately restored. The movements of the galvanometerneedle were rendered visible in these experiments by lookingthrough a piece of wide mesh wire gauze with a telescope.The respective position of the things was also reversed ; thatis to say, a Kuhmkorff coil and a periodically dischargedLey den jar were placed inside, and the sensitive substanceoutside, the box, with the same results. In some later experiments with a larger metallic case(Fig. 57), and with the Daniel cell, sensitive substance, delicategalvanometer, and Wheatstone Bridge placed inside, I found. Fig. 57. that a double casing was necessary in order to absolutelysuppress all effects. A glass covering afforded no protection. Considerations on the Mechanism of the Effects Produced.—What conclusions are we to draw from the experimentsdescribed ? The substances employed in these investigationswere not conductors, since the metallic particles composingthem were separated from each other in the midst of aninsulating medium. It was not surprising that currents ofhigh potential, and especially currents induced by discharges, should spark across the insulating intervals. But as theconductivity persisted afterwards, even for the weakest thermo-electric currents, there is some ground for supposing that theinsulating medium is transformed by the passage of the BBANLYS EXPERIMENTS. 10? current, and that certain actions, such as shock and rise oftemperature, bring about a modification of this

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• bookcentury1900
• bookdecade1900
• bookidsi
• booksubjectelectricity