Dead fish are frequently thus luminous, and brilliant phosphorescence is often an accompaniment of decomposition of both animal and vegetable matter. A few decaying potatoes will often light up a corner of a cellar which is dim by daylight, and an instance is on record of a certain cellar full of these vegetables giving off such a flood of light as to lead observers to suppose that the premises were on fire. Many animals, and especially fishes and insects, possess luminous properties. The familiar examples of the glowworm and fire-fly hardly need be mentioned. Then there are the big lantern-flies, with their luminous heads; and brilliant snapping beetles of the South, with their two glowing headlights, so effectively employed as ornaments for the hair and otherwise in the toilet of the Cuban belle. But the sea is the home of luminous life. From the diminutive myriads of the _noctiluca_, which sets the sea aflame, to the numerous larger finny tribes, the ocean is peopled with animal life, which, though dwelling in depths scarce reached by the faintest gleam from the sun, swim about enveloped in their self-illumined halo. While all these phenomena come under the general term of phosphorescence, the inference of the presence of phosphorus is incorrect; many substances without a trace of phosphorus in their constitution emit light with equal brilliancy. The well-known commercial article called "luminous paint" is an apt example, which, while containing no trace of phosphorus, glows like fox-fire at night, especially after having been exposed to the sun's rays during the day, giving forth in the dark hours the light which it has thus absorbed, and being thus of utility in its application to clock faces and match-boxes. Calcined lime and burnt oyster-shells, in combination with certain acids, become luminous at night by the similar power of absorption and transmission of light vibration which is supposed to be the secret of much of the so-called phosphorescence. But fox-fire is believed to be of a different nature, more chemical in its character, and usually emanates from a fungus, either visible in the form of mould or toadstool, or existing as an almost invisible essence which saturates the decaying wood, a species known as _Thelaphora cerulea_ being credited with most of the luminous manifestations. Fox-fire is occasionally put to a cruel utility by hunters in association with the "salt-lick" for deer. Salt is scattered in a selected spot, and a piece of fox-fire adjusted beyond it in direct line of the aim of the rifle, which is securely fixed in place. The sudden obscuration of the light is a sufficient signal for the still-hunter, who has only to pull the trigger to secure the game, even though the latter be entirely hid in the darkness.