March 1, 1893.] 



KNOWLEDGE 



47 



sentence, " They fly from us when we run to meet it." The 

 Welsh corpse candles and the luminous insects wind up 

 appropriately a series of mistakes. 



On turning to so respectable a publication as the EmjUsh 

 CijcJiquvdia (Arts and Sciences Division), 1860, the ifinis 

 fittuus is described as a meteor resembling a tlame, which 

 is vaguely said to do a number of things, and may be seen 

 over marshes and burial grounds ; and the case is related 

 in which a weak blue flame came up from the sea, and 

 burnt some ricks of hay. It is also stated that " such 

 meteors are most usually witnessed during a fall of rain 

 or snow." After referring to some other cases, the writer 

 remarks, " Little confidence can be placed in the descrip- 

 tions given of them, as few persons have been able to 

 examine them with due attention ; and commonly they 

 have been observed under the influence of an ill-regulated 

 imagination rather than a philosophical spirit." That 

 such meteors are due to phosphuretted or carburetted gas 

 is termed " a plausible hypothesis," but " there is a great 

 dearth of satisfactory observations on moving lights seen in 

 Nature, and the entire subject is at present in obscurity." 



In the ninth edition of the Ci/clopmlia Bntannica the 

 subject is treated, oddly enough, under Phospliorescence, 

 which is said to be a name " given to various phenomena 

 due to different causes, but all consisting in the emission 

 of a pale, more or less ill-defined light, not obviously due 

 to combustion." It is stated that the ii/nis fatuus, as seen in 

 marshy districts, has given rise to much difference of 

 opinion. Kirby and Spence suggested that it might be 

 due to luminous insects, "but it is more reasonable to 

 believe that the phenomenon is caused by the slow (?) 

 combustion of marsh-gas." 



In Clnimhers's Cyclopadii/ (a Dictionary of Universal 

 Knowledge), new edition. Vol. VI., 1890, the article Iijnis 

 Fatuus seems to have been entirely derived from the article 

 Iniichter in the Kunversations-Lericun. In this there is 

 the same uncertainty in the treatment of the subject, and 

 the same confusion as in the earlier writers, arising from 

 the application of the same term to meteors of very 

 different origin. The article begins by stating that the iynis 

 fittuus " is a luminous appearance of uncertain nature, 

 which is occasionally seen in marshy places and church- 

 yards. The phenomenon has been frequently described, 

 but it has been observed so rarely in favourable circum- 

 stances by scientific men, that there is no satisfactory 

 explanation." The theory that the meteor is due to 

 ignited marsh-gas is dismissed as untenable, because the 

 gas does not ignite spontaneously. The more plausible 

 suggestion, that it is due to phosphuretted hydrogen, which 

 ignites on contact with oxygen, is also rejected, on the 

 ground that a German observer " passed his hand through 

 the luminous appearance, and felt no warmth " ; while 

 another German " held the metal tip of a walking stick in 

 the flame of a fixed i;/nis fatuux . . . for a quarter of an 

 hour, but the metal was not warmed." The luminous 

 appearances here referred to were evidently electrical, not 

 gaseous, as was also the meteor, which was seen to " bound 

 over the country like a ball of tire for half an hour at a 

 time." 



It is suflScieutly evident that the compilers of the articles 

 just quoted were not scientific chemists, nor had ever had 

 any experience in laboratory practice. They seem to have 

 derived their information from some of the older books of 

 science, in which certain natural phenomena are attempted 

 to be explained before the science of the subject had been 

 discovered. Thus, previous to Franklin's great discovery 

 of the identity of lightning with common or frictional 

 electricity, that brilliant meteor was supposed to be due to 

 the oil of plants evaporated during the heat of the day, 



and set on fire in the sky. Ignorant, too, of gases, they 

 could not explain phenomena due to that source. What 

 they wrote up to the science of their time they generally 

 wrote well, but they had the unfortunate habit of explaining 

 within the terms of their own knowledge what lay far 

 beyond it, and which it was the function of future men of 

 science to discover. Such a writer was Dr. Van Muss- 

 clienbroek. Professor of Mathematics and Philosophy in 

 the University of Leyden. His Latin treatise on Natural 

 Philosophy was translated by John Colson, M.A., F.R.S., 

 Lucasian Professor of Mathematics in the University of 

 Cambridge, and was printed for J. Nourse at the " Lamb," 

 without Temple Bar, 1744. The following paragraph is 

 copied from Vol. II., p. 291 : — 



" § 1329. n'timlering fires, or ignes falni, are of a round figure, in 

 bigness like the flame of a caudle, but sometimes broader, and lilio 

 bundles of twigs set on fire. They sometimes give a brighter light 

 than that of a wax candle, at other times more obscure, and of a 

 jiurple colour. Wheu viewed near at hand they shine less than at a 

 distauce. They wander about in the air, not far from the surface of 

 the earth, and are more frequent in places that are unctuous, muddy, 

 marshy, and abounding with reeds. They haimt burying jjlaces, 

 places of execution, dunghills. They commonly apjiear in summer, 

 and at the beginning of autumn. But in the country about Bononia 

 they are seen throuahout the whole year in a dark night. For there 

 in a cold winter, and when the ground is covered with snow, they are 

 in greater ])lenty than in the hottest summer. Those, also, arc 

 observed in winter which Grassendus says are seen at Rogon, a town 

 of Provence. They appear more frequently in hot than in cold 

 countries. In Italy, near Bononia, are the greatest, and in the 

 greatest plenty. Sometimes they vanish on a sudden, and presently 

 shine out in another place. They are generally at the height of 

 about six feet from the ground. Now they dilate themselves, and 

 now contract. Now they go on like waves, and rain, as it were, sparks 

 of fire, but they burn nothing. They follow those that run away, and 

 fly from those that follow them. Some that have been catched were 

 observed to consist of a shining, viscous, and gelatinous matter, like 

 the spawn of frogs, not hot or burning, but only shining, so that the 

 matter seems to be phosphorous, prepared and raised from putrefied 

 plants or carcases by the heat of the sun, wliich is condensed by the 

 cold of the evening, and then shines. Yet I do not think that the 

 matter of all is the same, for without doubt those of Bononia differ 

 from those of Holland. It is a mere fiction that these fires are evil 

 spirits, or wandering ghosts, misleading travellers out of mere spite, to 

 plunge them into ditches and bogs, as some trifling philosojihers have 

 told us." 



In the above passage there are some good descriptions 

 of low-lying meteors, but the writer cannot reconcile the 

 phenomena as due to one source, for he does not suppose 

 that "the matter of all is the same." With our present 

 knowledge it is easy to recognize, in his description, three 

 varieties of low-lying meteors, namely, the gaseous of two 

 kinds, and the electrical. On the present occasion we will 

 trace the history of the i<inis fatuus properly so-called, 

 reserving for another article the consideration of the other 

 two meteors. 



The first step towards a true explanation of the ujnis 

 fatuus was taken by Priestley, who in 1767 commenced his 

 " Experiments and Observations on different kinds of 

 Air," and thus laid the foundation of pneumatic chemistry. 

 Among his experiments are a considerable number on the 

 inflammable air produced during the decomposition of 

 various kinds of vegetable matter, and he says : " The air 

 from marshes also, which, with Sig. Volta, I doubt not 

 comes from putrefying vegetable substances, 1 have also 

 found to be equally permanent," that is, not absorbed by 

 water as in the case of fixed air. Volta distinctly stated 

 that the gas from marshes is the cause of the iijnis fatuus, 

 and that the gas is kindled by lightning or by an electric 

 spark. 



The next step was taken by the Abbe Bertholon, 

 Professor of Experimental Physics at Languedoc, and 

 member of various scientific societies. In 1787 he 

 published a work on meteors, containing a chapter on the 



