The emission of light rays by a substance not heated, but whose luminosity is due to the persistence of luminous vibration after light has fallen upon it.

A phosphorescent body, after exposure to light, is luminous itself. Phosphorescence may be induced by rubbing or friction, by heat, by molecular bombardment, as in Crookes' tubes, and by static discharge of electricity, as well as by simple exposure to light.

Another form of phosphorescence may be due to slow chemical combustion. This is the cause of the luminosity of phosphorous.

Phosphorescence of Plants

Mr. Hunt recounts these striking instances. The leaves of the œnothera macrocarpa  are said to exhibit phosphoric light when the air is highly charged with electricity. The agarics of the olive-grounds of Montpelier too have been observed to be luminous at night; but they are said to exhibit no light, even in darkness, during the day. The subterranean passages of the coal-mines near Dresden are illuminated by the phosphorescent light of the rhizomorpha phosphoreus, a peculiar fungus. On the leaves of the Pindoba palm grows a species of agaric which is exceedingly luminous at night; and many varieties of the lichens, creeping along the roofs of caverns, lend to them an air of enchantment by the soft and clear light which they diffuse. In a small cave near Penryn, a luminous moss is abundant; it is also found in the mines of Hesse. According to Heinzmann, the rhizomorpha subterranea  and aidulæ are also phosphorescent.—See Poetry of Science.

Phosphorescence of the Sea

By microscopic examination of the myriads of minute insects which cause this phenomenon, no other fact has been elicited than that they contain a fluid which, when squeezed out, leaves a train of light upon the surface of the water. The creatures appear almost invariably on the eve of some change of weather, which would lead us to suppose that their luminous phenomena must be connected with electrical excitation; and of this Mr. C. Peach of Fowey has furnished the most satisfactory proofs yet obtained.

Light From the Juice of A Plant

In Brazil has been observed a plant, conjectured to be an 36  Euphorbium, very remarkable for the light which it yields when cut. It contains a milky juice, which exudes as soon as the plant is wounded, and appears luminous for several seconds.

Light From Fungus

Phosphorescent funguses have been found in Brazil by Mr. Gardner, growing on the decaying leaves of a dwarf palm. They vary from one to two inches across, and the whole plant gives out at night a bright phosphorescent light, of a pale greenish hue, similar to that emitted by fire-flies and phosphorescent marine animals. The light given out by a few of these fungi in a dark room is sufficient to read by. A very large phosphorescent species is occasionally found in the Swan River colony.