In this way it might be
literally possible 'to hear a shadow fall athwart the stillness.'
He was not the first to entertain the idea, for in the summer of 1878,
one 'L. F. W.,' writing from Kew on June 3 to the scientific journal
NATURE describes an arrangement of the kind. To Professor Bell, in
conjunction with Mr. Summer Tainter, belongs the honour of having, by
dint of patient thought and labour, brought the photophone into material
existence. By constructing sensitive selenium cells through which the
current passed, then directing a powerful beam of light upon them, and
occulting it by a rotary screen, he was able to vary the strength of the
current in such a manner as to elicit musical tones from the telephone
in circuit with the cells. Moreover, by reflecting the beam from a
mirror upon the cells, and vibrating the mirror by the action of the
voice, he was able to reproduce the spoken words in the telephone. In
both cases the only connecting line between the transmitting screen or
mirror and the receiving cells and telephone was the ray of light. With
this apparatus, which reminds us of the invocation to Apollo in the
MARTYR OF ANTIOCH--
'Lord of the speaking lyre,
That with a touch of fire
Strik'st music which delays the charmed spheres.
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