. The science-history of the universe . imesas great as that which measured either path of the cross-ing signals. A few years later James Lindsay, a Scotch-man, repeated Morses experiments, but without knowingof them. In 1859 he read a paper before the British Asso-ciation on the subject of Telegraphing without Wires,*and among his hearers were Faraday and Lord Kelvin. A method of signaling without wires by means of theinductive effect of two parallel circuits was successfullyused by Sir William Preece in 1882. The principle ofthis method is as follows: If two loops of wire are placedparallel
. The science-history of the universe . imesas great as that which measured either path of the cross-ing signals. A few years later James Lindsay, a Scotch-man, repeated Morses experiments, but without knowingof them. In 1859 he read a paper before the British Asso-ciation on the subject of Telegraphing without Wires,*and among his hearers were Faraday and Lord Kelvin. A method of signaling without wires by means of theinductive effect of two parallel circuits was successfullyused by Sir William Preece in 1882. The principle ofthis method is as follows: If two loops of wire are placedparallel to each other and an intermittent current is passedthrough one of them, waves of magnetic flux are sent out,portions of which thread the second loop and by theirfluctuations produce currents in it which may be detectedby a telephone or other device. The strength of suchsignals falls off very rapidly from the source, and such asystem can only be made to operate over short distances. Preece constructed two parallel lines, one on the Eng-. WIRELESS TELEGRAPHY 3*3 lish coast and one on the Isle of Wight, the arrange-ment of which is shown in Fig. 48. It will be seen thatthe loop from which the waves emanate is formed by theline wire and the earth. The crowning achievement, however, was the work ofHertz, whose early death deprived the world of the aidof a most powerful brain. In 1886 Hertz discovered thatif a loop of wire having a small air-gap left in it were
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