170 THE CURIOUS LORE OP PRECIOUS STONES
been subjected to the most searching tests in order to determine their qualities in this respect.47
His interest in this field of research was greatly stimulated by a
fortuitous happening. In 1891 his wife, while hanging up a gown in a
closet one evening, saw that the diamond in a ring she was wearing gave
off a faint streak of light which was very noticeable in the dark, and
this fact led to a long series of experiments on the fluorescence,
phosphorescence, and triboluminescence of the diamond.48 More
than two centuries before, Robert Boyle made a similar set of
experiments at night with a diamond which must have been an Indian
stone, and which he describes as table cut, about one-third of an inch
long and somewhat less in width ; he remarks that it was a dull stone
of very bad water, having a blemish with a whitish cloud covering
nearly a third of the stone.49
The
"Journal des Sçavans" for 1739 gives certain tests of the luminous
quality of diamonds made by Mons. Du Fay. In order successfully to
observe this phenomenon, he prescribes that the experimenter shall
remain in a darkened room for fifteen minutes, taking the additional
precaution of closing one or both of his eyes. The diamond to be
tested should be exposed to the sun's rays, or to strong daylight, for
less than a minute, and when taken into darkness the luminosity, if
observable, lasts twelve
47 See
Kunz, " The Phosphorescence of the Diamond," Trans. Ν. Υ. Academy of
Sciences, vol. x, p. 50, 1890-91; Kunz and Baskerville, "The Action of
Radium, Actinium, Roentgen rays, and Ultra Violet Light in Minerals and
Gems," Science, vol. xviii, No. 468, pp. 769-783, December 18, 1903.
48 See page 172.
**
Boyle, " Works," London, 1744, vol. ii, p. 85. The experiments were
made October 27, 1663, and the results were communicated to the Royal
Society the next day, the diamond which had been used being shown to
the members at that time.
