'
Professor Bell has accomplished the curious feat of speaking along a
beam of sunshine 830 feet long. The apparatus consisted of a
transmitter with a mouthpiece, conveying the sound of the voice to a
silvered diaphragm or mirror, which reflected the vibratory beam
through a lens towards the selenium receiver, which was simply a
parabolic reflector, in the focus of which was placed the selenium cells
connected in circuit with a battery and a pair of telephones, one for
each ear. The transmitter was placed in the top of the Franklin
schoolhouse, at Washington, and the receiver in the window of Professor
Bell's laboratory in L Street. 'It was impossible,' says the inventor,
'to converse by word of mouth across that distance; and while I was
observing Mr. Tainter, on the top of the schoolhouse, almost blinded by
the light which was coming in at the window of my laboratory, and
vainly trying to understand the gestures he was making to me at that
great distance, the thought occurred to me to listen to the telephones
connected with the selenium receiver. Mr. Tainter saw me disappear
from the window, and at once spoke to the transmitter. I heard him
distinctly say, "Mr. Bell, if you hear what I say, come to the window
and wave your hat! " It is needless to say with what gusto I obeyed.
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