369. The last of the luminous meteors which we shall describe is the Ignis Fatuus, Will-o'-the-bush, Jack-with-a-lanthern, or Scoticè Spunkie. It is seen at night, generally in marshy places :

"Sometimes from rushy bush

To bush it leaps, or, cross a little rill,
Dances from side to side in winding race

-leading from the path

To faithless bogs, and solid seeming ways."

GRAHAM, British Georgics.

It appears upon dunghills and in grave-yards, flickering about with unsteady light, and receding from the observer on his approach. It has been remarked that this meteor occurs more frequently in the autumnal season than in the other months, probably because the circumstances which lead to its production are then developed most abundantly; and supposing it to be a gas of terrestrial origin, the pressure of the air at that period of the year by its frequent changes, may be favourable to the escape of the elastic fluid. The ignis fatuus is generally of a pale bluish colour, and seems brightest at a distance. Newton defined it as "a vapour shining without heat."

370. The Ignis fatuus was finely seen near Birmingham' on December 12. 1776. Dr Derham once observed it play around a thistle, but it flitted away by the movement of the air when he got within a few feet of it. A curious appearance of the meteor was witnessed by Dr Shaw' in one of the valleys of Ephraim, where it seemed to run along the ground for upwards of an hour, and expanded itself over two or three acres of the adjacent mountains. It appeared about 1480-81 upon the continent more frequently than ever previously in the recollection of the inhabitants-at that time the plague was raging in Europe. Beccaria describes it as seen at Bologna, where, about 150 years ago, it was very common. It was nightly visible to the N. and E. of that city, and peculiarly brilliant to the east, in the fields of Bagnara He esti

3

4

1 Priestley, Exper. and Obs. on Air, append. vol. iii.

Trav. in Holy Land, &c.

4

• Phil. Trans.

Epidem. Mid. Ages,-Hecker.

mated the luminosity as equal to the light of an ordinary faggot one which accompanied a friend for a mile along the road, shone like a large torch. Its appearance was not constant; it came and went-rose and fell-would hover six feet from the ground-would contract its volume and expand -would separate and again unite-assuming the form of a luminous wave and dropping brilliant scintillations. M. Doe1 mentions a fine appearance of this meteor on the evening of May 26. 1821, in the marsh of the Chapelle-aux-Planches, in the Department of the Aube. It resembled a pyramid of pale red light, from ten to twelve feet high, so bright that one could read by it, but it had no heat. After half an hour, the mass of light broke into patches, which dispersed themselves over the marshy ground. Dr Quirino Barillic Filepauti2 mentions, that one evening Onofrio Zanotti observed this meteor issuing from the ground between the paving stones of the street of Lungo-Reno, in Bologna, near the house of Professor Santini; it is stated too, and this is remarkable, that he felt the impression of heat. On one occasion he observed the meteor near the town, moving horizontally, and carried by the breeze to the banks of the Idice in Bolognese, where it disappeared. Another time, in October, as he was watching the ignis fatuus in the parish of San Donino, about two miles from the city, upon a field in which there is a pool, the meteor appeared about 11 P.M. At the distance of twenty feet it presented the usual appearances, with a slight emission of smoke; it was moving slowly from S. to N., but changed its direction on being approached, ascended, and vanished--not, however, till a long rod previously prepared with some flax tied to the end, was thrust into the flame and kindled. That heat should have been experienced and flax ignited is so remarkable as to cast some doubts upon the correctness of the observation: we should like to know of a similar result before dismissing the generally received opinion that this meteor is merely luminous.

371. Reflecting upon this subject, many instances start to mind, which shew that though light and heat are intimately

Jour. de Phys. tom. xciii. p. 236, Sept. 1821.

2 Annali di Fisica.

connected, the former may exist without the other being appreciable. There are many illustrations of their separate existence, i. e. of the absence of the sensible properties of caloric in light-giving bodies, we would distinguish between the luminosity of living bodies, and that which appears on organic matter deprived of vitality. This property is possessed by several of the Annelides, e.g. the Nereis noctiluca (Lin.), and others more recently detected.' It is met with in many of the Mollusca, particularly those belonging to the Acephala tunicata, as the Pyrosoma of various species, and Salpa ; in the bivalve molluscs, the Pholas; likewise in some belonging to the great divisions Cephalopoda and Pteropoda. We find the same quality possessed by several of the Crustacea, e. g. the Cancer pulex (Lin.), c. fulgens (Banks). Certain fish are supposed to be luminous, as, for example, a scopelus, but it is uncertain if the property is not due to phosphorescent animalculæ attaching themselves to their scales. It is an attribute belonging to many of the Zoophytes, particularly to most of the medusa; among the acalephes properly so called, to the noctiluca, and beroë-the cilia of the Cestum veneris are vividly luminous, and exquisitely beautiful as it glides along like "an undulating flame several feet in length;"-among the polypes, to the Sertularia pumila, and other species; to the pennatula; to the flustra, the membranipora, and others.

"Awaked before the rushing prow,
The mimic fires of ocean glow,

Those lightnings of the wave;

Wild sparkles crest the broken tides,
And, flashing round the vessel's sides,
With elfish lustre lave;

While, far behind, their livid light

To the dark billows of the night

A gloomy splendour gave."

SIR WALTER SCOTT,-Lord of the Isles.

Phosphorentia maris quatuordec. lucescent. animalc. novis spec. illust. Genevæ, 1805.

2 See Dr Johnston,-Hist. Brit. Zoophytes; Thompson,-Zoolog. Research.; Cuvier, Anim. King.-Griffiths; Tiedemann,-Comp. Physiol. i. 259; Ed. New Phil. Jour. vol. v.; Mag. Nat. Hist. vols. iii. iv. v. vii. ix.; Proceed. Zool. Soc. Jan. 1837; Dr Fleming,-Hist. Brit. Animals; Dr Macculloch,-Hist. Western Islands of Scotland. Mag, of Zool. and Bot. vol. i. p. 492.

4

Rymer Jones,--Outline of Anim, Kingd. p. 77.

Two species of Myriopoda or centipedes are luminous,―the Geophilus phosphoreus of Asia, and the G. electricus of England.' This property is met with in many of

"The winged lights

That spangle India's fields on showery" nights."

The beetles or coleopterous insects furnish the largest number of these light-giving creatures. The fire-flies of Guadaloupe and other places, especially the Fulgora lanternaria (Lin.), a hemipterous insect three inches long, and native of South America, the F. candelaria of China, the F. diadema and pyrrhorhynchus of India. Above twenty species of the Elaterida are luminous; the best known are the Elater ignitus, and noctillucus or cocuyos of the West Indies. Humboldt,3 describing the effects produced by them, says, "it seemed as if the starry firmament reposed upon the Savannah!" He mentions that they are used as lamps when confined within a calabash pierced with holes, and instances the case of a young woman of Trinadad, who, when at sea, suckled her child by the light of these insects. Another family, the Lampyrides, contains nearly two hundred species having the same property; of them the Lampyris noctiluca (Lin.), or glowworm, is a familiar example; the Pygolampsis italica affords another illustration. The same curious property is possessed by the Vegetable Kingdom; thus some of the fungi are phosphorescent, the rhizo-morpha of mines, vaults, and cellars, the Agaricus olearius of De Candolle, also a large species found in Australia, and described by Drummond. Gardner' mentions having unexpectedly met with another luminous fungus in Brazil, called by the natives Flor do Coco, growing upon the decaying leaves of a palm, and giving out a bright pale greenish light, similar to that emitted by a cluster of pyrosomæ. He found children at play with this fungus in the streets of the Villa de Natividade. The same quality has re

1 Leach,-Linn. Tr. xi. 384; Scolopendra elect.-Geoffroy, Hist. des Insects, ii. 676, 5.

2 Carreri, Trav.; Moore,- Lallah Rookh,

4 Trav. in Brazil, p. 346.

a Person. Nar.

cently been discovered in a tree found in the jungles of Burmah, and lately shewn to the Asiatic Society. The nasturtium and some other garden flowers are said to be phosphorescent. Even certain secretions of the body are found occasionally to be luminous. Is this phosphorescence a quality or attribute of certain matters, or does it depend upon new combinations of their chemical constituents ?-does it arise from light developed by unknown cause, from molecular structures in which it has been hid ?-or are both in operation? This is an inquiry eminently suggestive. The phosphorescence of certain fish, seems to arise after death and before decomposition has fully set in, from the evolution of phosphuretted hydrogen; but this gas becomes extinguished as putrefaction advances, probably by the disengagement of ammonia, and its union with the other gas. Phosphuret of nitrogen is luminous likewise when in contact with the atmosphere. On the electrical theory of phosphorescence, we refer to the work of Becquerel.2

372. Returning from this digression to the ignis fatuus, which, true to its character, has flitted from us when we wished to make its most intimate acquaintance, we would observe, that its particular cause is unknown. Some assign to it an electrical origin; others believe it to arise from chemical products of decomposition, in which case it is most probably phosphuretted hydrogen, a gas spontaneously inflammable in the presence of atmospheric air. The suggestion of this gas as an explanation of the meteor, recals the chimera of sepulchral lamps perpetually burning. The sober matter-of-fact man may join the sceptic in rejecting the fable, though told by Licetus, of the unextinguishable lamp in the tomb of Pallas, the hero of the Mantuan bard,' discovered about the year 800, after being shut up nearly 2000. Are we to accept the account of the burning lamp of Olybius, encased in its double urn; or that of Tulliola, which was said to be found

1 Jurine,-Bib. Med. Nov. 1813; Guyton-Morveau,-Annal. de Chimie, tom. lxxxix. p. 182; Reisel,-Miscel. Acad. Nat. Curios. Dec. 1, An. 6 and 7, p. 280; Willis,--Urin. Dis. 1838, p. 134.

2 Traité de l'Elect. et du Magnetisme; Annal. de Chimie et de Phys. passim. Fortunio Liceti de Reconditis Antiq. Lucernis; Octavio Ferrari,-De Vet. Lucer. Sepulc. 4 Æn. vii.