‎"BELL, ALEXANDER GRAHAM. - THE PHOTOPHONE AND SPECTRAL ANALYSIS.‎
‎Sur l'application du photophone à l'étude des bruits qui ont lieu à la surface solaire. Note présentée par M. Janssen au nom de Alex. Graham Bell.‎

‎(Paris, Gauthier-Villars), 1880. 4to. No wrappers. In: ""Comptes Rendus Hebdomadaires des Séances de L'Academie des Sciences"", Tome 91, No 18. Pp.(698-) 736. (Entire issue offered). Bell's paper: pp. 726-727.‎

Reference : 48148

‎First printing of the paper in which Bell speculates how his and Tainter's invention of the Photophone or Radiophone could have a wider use. He pondered the photophone's possible scientific use in the spectral analysis of artificial light sources, stars and sunspots. He later also speculated on its possible future applications, though he did not anticipate either the laser or fiber-optic telecommunications:""Can Imagination picture what the future of this invention is to be!.... We may talk by light to any visible distance without any conduction wire.... In general science, discoveries will be make by the Photophone that are undreamed of just now."" Not long after its invention laboratories within the Bell System continued to improve the photophone in the hope that it could supplement or replace expensive conventional telephone lines. Its earliest non-experimental use came with military communication systems during World War I and II, its key advantage being that its light-based transmissions could not be intercepted by the enemy.‎