When quicklime is mixed with essential oil, and brought in contact with water, spontaneous combustion is said to take place.
Fluor or Derbyshire spar, (fluate of lime), when pulverized and heated to 212° Fahr., and then removed to the dark, is very luminous. If writing be made on a copper or iron plate, with thin mucilage or white of egg, and powdered fluor spar, sprinkled on it; when the plate is removed to a gentle coal fire, the delineated objects will become luminous, and opaque again when the plate becomes cold. The lapis lazuli has the same effect.
The phosphoric substances, which become luminous by attrition or percussion, are numerous. Homberg's phosphorus, which is nothing more than calcined muriate of lime, is of this character. When struck it emits light. Without either light or fire, a number of bodies will give out light. Flints, and other siliceous stones, struck against one another, appear luminous in the dark. Various other minerals have the same property. Wedgwood (Phil. Trans. 179,) Coates (Nich. Jour. 1799,) Westrumb (Crell's Chem. Annals, 1784,) have written on this subject; to which enumeration we may add the interesting remarks of Dr. Hulme, (Phil. Trans. 1800,) and the observations of Cabarris, in his Memoir, read before the National Institute.
It may be sufficient to remark, that the shell-fish called pholas; the meduca phosphorea, and other molluscsæ; several insects of the species fulgora, or lantern-fly; the lampyris, or glowworm; the scolopendra electrica; the cancer fulgens; the medullary substance of the human brain, &c. are all phosphorescent.
M. Dessaignes (Bulletin de la Société Philomatique, Octobre, 1810) made a number of experiments on solid, liquid, and aeriform bodies, relative to the disengagement of light by compression. Among other conclusions, he adds, that water is the cause of the spontaneous phosphorescence of bodies, such as quicklime, Canton's phosphorus, dry muriate of lime, &c. all which, when brought in contact with water, emit light, which he attributes to the consolidation of that fluid. The absorption of moisture, and its subsequent consolidation, may, in some instances, give rise to luminous appearances.
The lapis solaris, Bolognian stone, or the present sulphate of barytes, was discovered in 1602, by Casciorolus, a shoemaker of Bologna. He came to Scipio Begatello, who at that time was particularly known by his attachment to the art of gold-making, and showed him this stone, under the mystical name of lapis solaris, on account of its attracting the golden light of the sun, and its boasted fitness for converting the semi-metals into gold, the sol of the alchemists!
Dr. Brewster (Edinburgh Philosophical Journal) made a number of experiments on the colour and intensity of light, evolved by different minerals, by which it appears, that the yellow sulphate of barytes gives a pale light, while fluate of lime, a blue and green light. Cellini (Treatise on Jewelry, published near the beginning of the 16th century) was the first who observed the phosphorescence of minerals; it does not appear that he knew of the Bolognian stone. Grimshire (Nicholson's Journal, 8vo. vols. 15, 16, 19,) made a number of experiments on the emission of light by bodies, when subjected to the electrical influence; and, when thus treated, sulphate of barytes gave a brilliant green light.
The cawk of the miners, as it is also a sulphate of barytes, phosphoresces when previously exposed to heat.
There are two water fountains, both set in motion by the action of heat on confined air, which, as it expands, forces the water from an under vessel in jets. The first is called the illuminated fountain, and plays when the candles are lighted, stopping when they are extinguished. The other is a fountain, which acts on the same principle, but by the heat of the sun. The effect of the first is more or less considerable according to the pressure of the air upon the water, and consequently, to the degree of rarefaction which the air undergoes.