'
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 1879 Professor Hughes brought out his beautiful induction
balance, and the following year Professor Bell, who had already worked
in the same field, consulted him by telegraph as to the best mode of
applying the balance to determining the place of the bullet, which had
hitherto escaped the probes of the President's physicians.
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