sunshine. It appears from these experiments, that almost all inflammable
bodies possess this quality in a greater or less degree; white paper or
linen thus examined after having been exposed to the sunshine, is
luminous to an extraordinary degree; and if a person shut up in a dark
room, puts one of his hands out into the sun's light for a short time
and then retracts it, he will be able to see that hand distinctly and
not the other. These experiments seem to countenance the idea of light
being absorbed and again emitted from bodies when they are removed into
darkness. But Beccari further pretended, that some calcareous
compositions when exposed to red, yellow, or blue light, through
coloured glasses, would on their being brought into a dark room emit
coloured lights. This mistaken fact of Beccari's, Mr. Wilson decidedly
refutes; and among many other curious experiments discovered, that if
oyster-shells were thrown into a common fire and calcined for about half
an hour, and then brought to a person who had previously been some
minutes in a dark room, that many of them would exhibit beautiful irises
of prismatic colours, from whence probably arose Beccari's mistake. Mr.
Wilson from hence contends, that these kinds of phosphori do not emit
the light they had previously received, but that they are set on fire by
the sun's rays, and continue for some time a slow combustion after they
are withdrawn from the light. Wilson's Experiments on Phosphori.
Dodsley, 1775.

The Bolognian stone is a selenite, or gypsum, and has been long
celebrated for its phosphorescent quality after having been burnt in a
sulphurous fire; and exposed when cold to the sun's light. It may be
thus well imitated: Calcine oyster-shells half an hour, pulverize them
when cold, and add one third part of flowers of sulphur, press them
close into a small crucible, and calcine them for an hour or longer, and
keep the powder in a phial close stopped. A part of this powder is to be