sulphuret of barium; that is, sulphate of barytes,
or heavy-spar after calcination. Scipio Begatello,
the alchemist, also of Bologna, had a bit of this
light-bearing marvel brought to him by the old
cobbler; this Lapis solaris, which was heavy as
gold, attracted the sun, and shone like the sun
in the dark, and was thus evidently bound up
with the Sol of the fraternity: which Sol was
also gold. The cobbler showed it to some others;
so that the fame of the Bologna stone got spread
abroad, and was made one of the wonders of
the old city. This was in 1602, and is the
history of the Bologna stone as discovered by
Cascariolo the cobbler, and detailed by DR. PHIPSON,
in his charming little volume on Phosphorescence,
lately published. Years afterwards,
Marggraf made some pretty bright things by
pulverising barytine and mixing it up into a paste
with flour in the form of stars, or what form
soever he chose to employ, then heating the stars
in a closed crucible: which stars, if exposed to
the sun for a short time after, would light up in
the dark with marvellous radiancy and brightness.

In 1663, Robert Boyle, "the father of
English chemistry, and uncle of the Earl of Cork,"
going his way towards knowledge and the
future, found that the diamond was phosphorescent
after being exposed to the rays of
the sun. In 1675, Baudoin got a new
phosphorus out of calcined nitrate of lime. Nearly a
hundred years later, Canton's phosphorus—
three parts of calcined oyster-shells with one of
sulphur—was shown before the Royal Society
of London under various very lovely experiments.
Plaster of Paris, calcined with common
charcoal, and exposed to the sun, is also
phosphorescent; and walls lately whitewashed may
be seen shining with a steady glow-worm light
after exposure to the burning rays of a summer
sun. Indeed, many mineral substances are of
the light-bearing tribe. Among them some
varieties of fluor-spar, carbonate of lime, burnt
oyster-shells, pearls, phosphate and arseniate of
lime, some diamonds, and the beautiful variety
of fluor-spar known as chlorophane, which, when
of the noblest kind, is luminous in the dark by the
mere heat of the hand—of a lower order of merit,
at good warm summer heat, say from sixty to
eighty Fahrenheit.

Electricity and heat have both much to do
with creating phosphorescence. A slight shock
passed through an exhausted substance, or even
exposure to the electric light, will restore the
light that has departed; and heat is one of the
prime agents. Fluor-spar, lime, sulphuret of
calcium, diamonds, &c., pulverised and thrown
on a heated surface become brilliantly luminous;
fluor-spar the most so. Thrown on to heated
mercury, into boiling water, or on a hot shovel,
it becomes exceedingly bright. But there is
one curious thing about it. A perfect crystal
of fluor-spar will not become phosphorescent by
heat alone, unless one surface be slightly roughened
on sandstone: diamonds, on the contrary,
will not become phosphorescent unless perfectly
polished. Certain diamonds, which will not
shine by heat alone, will by electricity;
certain non-phosphorescent bodies can be made
luminous by heat, if previously electrified. Of
these, are some marbles, apatites, and others of
the same class. When exposed to the light
they lose this quality, but retain it if kept in
the dark. Metallic arsenic, and native sulphuret
of antimony (stibine, not antimony pure),
become phosphoric when heated to a dull red heat,
and shine with a yellow-white light. Gold,
copper, and silver, are all phosphorescent when
melted on charcoal; so is the mineral called
lepidolite; so is sulphate of quinine, and
sulphate of cinchonine—also by heat but not
by exposure to light; so is paper. Common
salt is phosphorescent at a great heat: and
chloride of calcium, that has been melted and
then rubbed, glows with a greenish light. This
is called Hornberg's phosphorus, because first
observed by him. The crystals of nitrate of
uranium are strikingly luminous when shaken
up in a bottle; and many crystals give out light
at their point of cleavage. When mica is broken,
a spark flashes out, and the separated plates are
found to be electric: one positive and the other
negative. So it is with feld-spar. Boracic
acid, melted in a crucible and then cooled, splits
as it cools and sends out faint flames; when
vanadic acid is melted, it also crystallises in
cooling: the crystals glowing with a red
phosphoric light. Vanadium, whence the acid, is a
white metal, a kind of underdone silver, found
in 1830 by Sefström, the Swedish chemist, in a
certain soft iron remarkable for its ductility;
and called by him after some heathenish old
Scandinavian idol, unknown to general fame.
So also, when phosphate of lime is melted, it
cools into phosphorescent crystalline beads, very
beautiful to behold. Transparent feld-spar is
luminous when pounded; so is sugar, which
makes quite a grand display when pounded
rapidly in a mortar in the dark, until the whole
mass seems to be a small sea of flame. So says
Dr. Phipson. By practical experiment, I, the
compiler of this paper, know nothing.

Water freezing very rapidly, gives out sparks
at the moment of passing from water to ice.
This was a discovery made by Professor Pontus
in 1833. Blend, with very slight excitement;
quartz, giving when rubbed the odour of ozone;
flint, borax, sugar, sulphur, are all luminous
when slightly rubbed in the dark; but the most
phosphoric of all substances is phosphorus itself,
which is luminous at any temperature above
zero. Below that, its light is put out.
Phosphorus can make six hundred thousand parts of
spirits of wine luminous with one part of itself,
and gives light to water in which it is kept.
Phosphuret of calcium thrown into water, sends
off bubbles of phosphuretted hydrogen gas, which
take fire in the atmosphere and give off rings of
white smoke, beautifully luminous, and making
an exceedingly lovely experiment. Potassium is
luminous when first exposed to the air. M.
Petrie covered a stick with beeswax, then cut it
in two parts, and each segment was phosphorescent
when cut. Potassium has a reddish
light, but burns with a purple flame in water;