Kirby's Wonderful and Scientific Museum, 1820

R. S. Kirby (1820), Kirby's Wonderful and Scientific Museum; p.263-9.


Account of the singular phenomenon commonly called ignis fatuus, Will-of-the-wisp, or Jack-o'-lantern.

These meteors are in fact nothing more than a real exhalation from the earth, as vaporous gas, or some other weaker substance, combined with the matter of light and heat, or even with both mixed, which has been elicited either from animal, vegetable, or mineral substances. They are at all times of a rare and subtle matter, and are mostly generated in low marshy plains, though, at times, but rarely, they may be seen on the tops of lofty mountainous tracts, where boggy springs are situated. The Editor has often seen them on Dartmoor and Exmoor, in Devon, and twice on the side of a mountain in the Highlands of Scotland. To the weak-minded and superstitious, they are a source of real terror; and, it is probably, they they have frequently seduced a timid and benighted traveller into the fangerous bogs and quagmires where themselves have been generated. Goldsmith, in his beautiful poem of the Hermit, alludes to this fact in the following couplet:

"Forbear, my son, the hermit cries,
To tempt the dang'rous gloom
For yonder faithless phantom flies,
To lure thee to thy doom."

The luminous exhalations are designated by the learned, Ignes Fatui, or Mock Fires—and by the vulgar, Will o'-the-Wisps, and Jack-o'-Lanterns; and when seen at sea, or near the coast, Mariners' Lights, or St. Helmo's Fires.

To account for the true cause of these singular appearances, has occupied much of the time and labour of the most skilful naturalists and philosophers in former times, but their explanations have not been attended with success. From the present state of knowledge of natural philosophy, we find it not difficult to be either given or comprehended, and we are not a little astonished to find our early philosophers travelling to Italy, and other parts, for documents which they might have found even near their own fire-side.

For the amusement of our readers, we shall extract some of their vague opinions from the Philosophical Transactions of their day:—The Rev. Mr. Dereham, and Sir Thomas Dereham, seen to have been the most successful in describing it. Mr. F. Willoughby and Mr. Ray, with others, think the Ignis Fatuus are only the shining of a great number of the male glow-worms in England. Others contend, that it must in Italy be the pyrustæ (a species of fly,) which are numerous in June and July, flying about at night-fall. Sir T. Dereham says, there pyrustæ are called lucciole, i.e. small lights, and that they are not the farfalls, as Mr. Ray thought, which are butterflies. The Rev. Mr. Dereham has reason to think, that insects are not concerned in the ignes fatui, from the following observations, the first made by himself, and the others received from Italy, by the favour of Sir Thomas Dereham.

Dr. Dereham relates, that in a valley between rocky hills, which he suspected might contain minerals, in some boggy ground, near the bottom of those hills, he saw an ignis fatuus in a calm dark night; he got up to within two or three yards, and viewed it with all possible care. He found it frisking about a dead thistle growing in the field, till a small motion of the air made it skip from place to place.

It appeared like a complete body of light without any division, so that he was sure it could not be occasioned by insects, but a fire-vapour.

He admits, the male glow-worms emit their shining light as they fly, by which means they discover the females; but never observed them fly together in such great numbers, as to make a light equal to an ignis fatuus.

As to the communications from Italy, it is observed:— These lights are very common in the plains in the territory of Bologna, and are called cularsi, perhaps from some fancied similitude to those birds; the belly and other parts of which are resplendent, like our shining flies. They are most frequent in watery and morassy ground, and there are some such places, where they might be seen almost every night; some of them giving as much light as a lighted torch; and some of them no larger than the flame of a common candle. All of them have the same property in resembling, both in colour and light, a flame strong enough to reflect a lustre on the objects around. They are continually in motion, but this motion is various and uncertain. Sometimes they rise up, at others they sink. Sometimes they disappear of a sudden, and appear again in an instant, in some other place. Commonly they keep hovering about six feet from the ground. As they differ in size, so also in figure, spreading sometimes pretty wide, and then again contracting themselves; sometimes breaking to all appearance into two, then meeting again, and appearing as one; then floating like waves, and dropping sparks as if out of a fire. And that they are observed more frequent in the depth of winter, when the ground is covered with snow, than in the hottest summer; that it has been observed, that they throw a stronger light in wet weather than in dry; the wet having no effect on it; and yet nothing was ever observed to be set on fire by it; and he was assured, that there was not a dark night throughout the whole year, in which they were not to be seen.

M. Beccari observes, he found these lights very frequent about rivers and brooks, and says—"An intelligent gentleman, travelling sometime in March, between eight and nine in the evening, in a mountainous road, about ten miles south of Bologna, perceived a light which shone very strongly, by a river called Rioverde, on some stones which lay on its banks. It seemed to be about two feet above the stones, and not far from the water of the river. In figure and size it had the appearance of a parallelopiped, somewhat more that a foot in length, and half a foot high, the longest side lying parallel to the horizon. Its light was so strong, that he could plainly discern by it part of a neighbouring hedge, and the water of the river—only in the east corner of it the light was rather faint, and the square figure less perfect, as if it was cut off or darkened by the segment of a circle. On examining it a little nearer, he was surprised to find that it changed gradually from a bright red to a yellowish, and then to a pale colour, in proportion as he drew nearer; and when he came to the place itself, it quite vanished. Upon this, he stepped back, and not only saw it again, but found that the farther he went from it, the stronger and brighter it grew. When he examined the place of this luminous appearance, he could perceive no smell nor any other mark of actual fire." This same observation was confirmed by another gentleman who frequently travels that way, and who asserted, that he had seen the very same fire five or six times in the spring and autumn; and that it always appeared in the shape, and in the very same place. One night, in particular, he observed it come out of a neighbouring field, and settle in the same place.

Dr. St. Clair speaks of the same flame, and says corn grows within a few yards of it, and he conjectures the flame arises from a vein of bitumen or naphtha.

The opinion of the learned of the present day, respecting these singular exhalations, is, that the principal source of these meteors is to be sought for in the light exhaled by the decomposition of animal and vegetable matter, magnified and deepened in hue by the vapoury haze of the atmosphere of the moist and swampy low lands, in which they are chiefly met with, and which, in consequence of their moisture and swampiness, are particularly favourable to the process of decomposition.

Thus, they say, may be accounted for those meteors that evince no sensible heat during their illumination, for the light exhaled or thrown off from these substances possesses no sensible heat whatever.

It, however, is acknowledged, that a greater or less degree of heat, a strong proof of actual, though slow combustion, has been evinced, during the existence of these phenomena; as, also, that they have extended more widely than any local decomposition would induce us to expect, and that they have even appeared to change their situation, and to dance from place to place.

A modern philosopher says, "To explain meteors of this kind, it is only necessary to observed, that the earth is perpetually exhaling a variety of inflammable gases, and other materials, as hydrogen gas, or inflammable air, phosphorus, carbonic acid gas, and, occasionally, sulphureous vapours; at times, separately, at others, in a state of union; and that the most active of these are particularly evaporating in the low stagnant marsh grounds, where these luminous meteors chiefly make their appearance, and may at any time be collected with the greatest ease, by placing over the surface of the soil an inverted glass tumbler. Now, although these gases will not spontaneously inflame in the ordinary temperature of the atmosphere, yet they readily inflame from a great variety of natural causes to which they are perpetually exposed. Electricity may be a common cause of such inflammation. The heat generated during the decomposition of the animal or vegetable materials that may be locally decomposing, may be far more than sufficient for that purpose, for we know it to be sufficient to ignire hay-stacks, when the grass has been put together too damp, and it is not improbable that some of these materials may catch the illumination as from a candle, from a body in the immediate vicinity that is in the act of spontaneous illumination.

Now the ball, or general mass of inflammable vapour, being once lighted or inflamed from whatever cause, will continue to burn so long as its inflammable principle remains, and its combustible power may be more or less, in proportion to its purity; whence, in some instances, it may pour forth light, with little or no sensible heat; in others, the heat combined with it may be sufficient to produce slow combustion like that of a dunghill; and in others, palpable and rapid flame. From the levity of the illumined or burning vapour, it must necessarily change its place in various instances, according to the current of air which it either finds, or by burning, makes for itself; hence it must appear to move in various directions, upwards and downwards, to the right and to the left; it will seem to advance and then to recede, from object to object, in a constant motion or dance before the spectator, according to the motion of the current of air that operates upon it, while its dimensions and colours must vary according to the varying density of the fog or haze thhrough which, in different places or situations, it is seen, or according to its actual increasing or diminishing and decaying bulk.

Sean B. Palmer