WIRELESS TELEPHONY FESSENDEN. 165 



Sir Oliver J. Lodge on June 1, 1894, delivered a. lecture before the 

 Ro3^al Institution." In this remarkable lecture Lodge described 

 among other things the following : 



1. The filings coherer. 



2. The filings coherer in hydrogen under reduced pressure (this 

 in a note added July, 1894). 



3. The automatic tapper back for the coherer. 



4. The metallic reflector for focusing the Avaves. 



5. The connection of the coherer to a grounded conductor, i. e., a 

 gas-pipe system. 



6. The method of making the coherer so connected respond by 

 setting up oscillations in a separate grounded system, i. e., a hot-water 

 pipe system, in another part of the building. 



7. The method of detecting distant thunderstorms b}^ connecting 

 the coherer to a grounded gas-pipe system. 



In this lecture Professor Lodge stated that in his estimate the 

 apparatus used would respond to signals at a distance of half a 

 mile. 



Early in 1895 Professor Poj^off,'' of Cronstadt, Russia, constructed 

 a very sensitive filings coherer, one form of which was used in some 

 surveying experiments by the Russian Government," consisting of 

 iron filings suspended by a magnet and resting upon a metallic plate 

 or cup. Other forms consisted of filings in glass tubes with platinum 

 electrodes. He used early in 1895 the automatic tapping back 

 mechanism and substituted for the galvanometer an ordinar}^ tele- 

 graphic relay. He operated this apparatus at a distance by means 

 of a large Hertzian radiator. One terminal of his coherer was con- 

 nected to a conductor fastened to a mast about 30 feet high on the 

 top of the Institute building, and the other terminal of the coherer 

 was gi'ounded. 



At the conclusion of his paper, which is dated December, 1895, 

 Popoff made the following statement : 



In conclusion I can express the hope that my apparatus, with further im- 

 provements of same, may be adai)te(l to the transmission of signals at a distance 

 by the aid of quick electric vibrations as soon as the source of such vibrations 

 possessing sufBcieut energy will be found. 



Among other experimenters who were working on this subject at 

 the same time may be mentioned Captain Jackson, of the British 

 Navy, and Mr. A. C. Brown. 



"^ Sir O. J. Lodge, " The work of Hertz," Proceedings Royal Institution, June 

 1, 1904, vol. 14, p. 321. 



* Journal Russian Physico-Chemlcal Society, vol. 27, April 25, 1895. 



" A. S. Popoff, "Apparatus for detection and registration of electrical vibra- 

 tions," Journal Russian Physico-Chemical Society, vol. 28, December, 1S95. 



