Thomas Lamb Phipson (1862), Phosphorescence; or, the emission of Light by minerals, Plants, and animals. London: L Reeve & Co. pp.63-69
Sean B. Palmer
I must now say a few words on that beautiful and mysterious production of light known as the Will-o'-the-Wisp or Ignis fatuus (feux follets of the French).
This phenomenon is generally attributed, by chemists of the present day, to the spontaneous inflammation of phosphuretted hydrogen gas. It is well known that one of the gaseous compounds of phosphorus and hydrogen takes fire as soon as it comes in contact with atmospheric air; and it is supposed that in certain circimstances the putrefaction of animal matters, containing phosphorus and sulphur, besides the four elements carbon, hydrogen, nitrogen, oxygen, and phosphate of lime, is accompanied by a production of this phosphuretted hydrogen gas. Will-o'-the-Wisp is observed in boggy lands, and where it is seen some animal or perhaps an unlucky traveller has been swallowed up in the mire.
The "corpse-candle" of the Welsh, which flickers over churchyards, is attributed to the above cause, and the same may be said of that mysterious production of light which occasionally takes place is dissecting rooms.
But no chemical experiment, made with organic matters, has yet been brought forward to prove the production of phosphuretted hydrogen with evolution of light by submitting these matters to the process of putrefaction. Indeed, I have shown, as will be stated in a future chapter, that the phosphorescence of dead fish does not appear to depend upon the presence of the chemical element phosphorus.
If, however, it were placed beyond doubt that the phenomenon of the Will-o'-the-Wisp or Ignis fatuus, depended upon the production and spontaneous inflammation of phosphuretted hydrogen, it could not be classed among phenomena of phosphorescence any more than the flames of certain fire-springs in the East, which are owing to the combustion of carburetted hydrogen or naphtha, and some of which, like the famous Lycian Chimæra, in Asia Minor, have been burning for several thousand years.
From some very interesting arguments brought forward in the last edition (in one volume) of Kirby and Spence's 'Introduction to Entomology,' it would appear probably that some cases of ignis fatuus might be attributed to certain luminous insects not yet known, which hover in clusters over marshy ground. These insects seem to belong to the genus Tipula (Gnat, "Daddy-Long-legs," etc.), if we are to judge from the hovering appearance of the light. Thus Dr. Derham, in the 'Philosophical Transactions' for 1729, describes an ignis fatuus, seen by himself, as flitting about a thistle.
Dr. Derham got within two or three yards of another ignis fatuus, in spite of the boggy nature of the soil. He states, however, that it appeared like a complete body of light without any division, so that he was sure it could not be occasioned by insects.
At the same time, it is evidence that no insects could produce the phenomeonon described by Dr. Weissenborn, in 1818, where the light travelled over a distance of half a mile in less than a second. (Mag. of Nat. Hist. N.S. i. 553.)
From these facts, it appears probably to modern philosophers, that there are two kinds of ignes fatui, the one referable to spontaneously inflammable gas, the other to luminous insects.
If phosphuretted hydrogen, or any other spontaneously combustible gas or liquid, caught fire upon a marsh where carburetted hydrogen (marsh gas) is constantly evolved, the latter would inflame also. (At Wigmore, in Herefordshire, and other places in England, carburetted hydrogen used to be so abundant in the ground that it was employed for lighting and cooking in the houses, as we learn from travellers is a common practice in China.)
In the valley of Gorbitz, Mr. Blesson discovered a light emanating from marshy ground. Remaining for some days near the place, in order to study the phenomenon as closely as possible, he found it was owing to an ignited gas, the faint flame of which was invisible during the day, but became gradually visible in the evening. The gas appears to have been carburetted hydrogen, or marsh gas. As he approached it, the flame receded, but he eventually succeeded in lighting a piece of paper by it.
According to some authors, Will-o'-the-Wisp may be seen at all seasons of the year; but a great number of persons I have questioned upon the subject all agree in stating that they have noticed it in autumn, or towards the end of autumn, and the beginning of November. It cannot be termed a common phenomenon, as many distinguished naturalists have never been able to observe it; it is not unfrequent in the north of Germany, and is often witnessed in the peat districts around Port Carlisle, in the Lowlands of Scotland, and in the swampy parts of the South of England, etc. It was seen by Mr. Warltire, in a very curious form, on the road to Bromsgrove, about five miles from Birmingham, as noted by Dr. Priestley in the Appendix to his third volume of 'Experiments and Observations on Air.' The time of observation was the 12th December, 1776, before daylight.
Some countries are very remarkable for this curious phenomenon; for instance, the neighbourhood of Bologna, in Italy, and some parts of Spain and Ethiopia. According to an account left us by M. Beccari, an intelligent gentleman travelling in the evening, between eight and nine o'clock, in a mountainous road about ten miles South of Bologna, perceived a light which shone very strangely upon some stones on the banks of the Rio Verde. It appeared as a parallelopiped of light, about a foot in length, and two feet above the stones. Its light was so strong that he could plainly see by it part of a neighbouring hedge and the water of the river. On examining it a little nearer, he was surprised to find that the light became paler, and when he came to the place itself, it quite vanish. No smell or other mark of fire was observed at the place where this light shone.
Another gentleman informed M. Beccari that he had seen the same light five or six different times, in spring and autumn, always of the same shape, and in the very same place.
Dr. Shaw, in his 'Travels to the Holy Land,' states that an ignis fatuus appeared to him in the valley of Mount Ephraim, and attended him and his company for more than an hour. Sometimes it appeared globular, at others it spread to such a degree as to involve the whole company in a pale, inoffensive light; then contracted itself, and suddenly disappeared, but in less than a minute it would appear again; sometimes running swiftly along, it would expand itself at certain intervals over two or three acres of the adjacent mountains.
Dr. Priestley has given an account of what some look upon to have been an artificial Will-o'-the-wisp. A gentleman, who had been making electrical experiments for a whole afternoon in a small room, on going out of it, observed a flame following him at some little distance. In this case, however, there seems to have been a difference between the artificial ignis fatuus and that met with in nature, for the flame followed the gentleman as he went out of the room, but the natural phenomenon generally recedes as we approach it.
It is a common practice, in chemical lectures, to imitate the Will-o'-the-wisp by throwing fragments of phosphuret of calcium into water, when flames arise, owing to the spontaneous combustion of phosphuretted hydrogen gas. But the imitation is very bad indeed, and can hardly be said to resemble the mysterious natural phenomenon, much less explain it. For my own part, I think the ignis fatuus to be sometimes the light from a burning gas, which light is invisible in the daytime, and at other times to be connected with those curious cases of luminous mists mentioned above, and in which electricity doubtless plays an important part.
The luminous appearances known in Scotland as Elf-candles belong either to this category of phenomena, or to that which will be treated of in a future chapter of this Work.