Gernsback, Hugo, 1884-1967, ed · New York : [s.n.] · leaf 12
hru the earth or water. Professor medium. The sound waves are picked up by ted intelligence over distances of fifteen to means of the same oscillator, or else by a Fessenden, as generally known, is the in- twenty miles when necessary, and one of the sensitive microphone, placed in a tank con-… … fnpyrlnht. 191K. by E- P. Co. By Means of the New Fessenden System Here Illustrated It Is Possible to Actually Talk Without Wires Thru the Earth Or Sea for Considerable Distances. Also, the New "Sound Direction Detector" Will Render the Accurate Locating of Enemy Mining or Sapping Operations a…
![An illustration from Histoire de mes ascensions : récit de vingt-quatre voyages aériens [1868-1877] (1880)](https://img.insideoutlibrary.com/img/200/ia-39002011210615.med.yale.edu-283-27.webp)
