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.'
The spectroscope has demonstrated the truth of the poet, who said that 'light is the voice of the stars,' and we have it on the authority of Professor Bell and M. Janssen, the celebrated astronomer, that the changing brightness of the photosphere, as produced by solar hurricanes, has produced a feeble echo in the photophone.
Pursuing these researches, Professor Bell discovered that not only the selenium cell, but simple discs of wood, glass, metal, ivory, india-rubber, and so on, yielded a distinct note when the intermittent ray of light fell upon them. Crystals of sulphate of copper, chips of pine, and even tobacco-smoke, in a test-tube held before the beam, emitted a musical tone. With a thin disc of vulcanite as receiver, the dark heat rays which pass through an opaque screen were found to yield a note. Even the outer ear is itself a receiver, for when the intermittent beam is focussed in the cavity a faint musical tone is heard.
Another research of Professor Bell was that in which he undertook to localise the assassin's bullet in the body of the lamented President Garfield. In
