62 



SCIENTIFIC NKWS. 



[Jan. 20, i£ 



it proved to be the insect in question. Mr. Main (" Maga- 

 zine of Natural History," N.S. I., p. 549) was told by a 

 farmer that he had encountered and knocked down 

 the luminous object, which he described as being exactly 

 like a ," Maggy-long-legs " (Tipula okracca) — an insect 

 especially abundant in boggy and marshy lands. I must 

 here admit that neither of the above insects are known to 

 be luminous. 



Dr. Dereham, an opponent of the insect theory (" Phil. 

 Trans.," 1729, p. 204), describes an Ignis fatiius which 

 he had personally witnessed as tlitting about a thistle — 

 a very likely action for an insect, though very unlikely 

 for a volume of inflammable gas. Mr. Sheppard informed 

 Dr. Kirby that, when travelling one night from Stamford 

 to Grantham on the top of a stage-coach, he observed 

 "for more than ten minutes a very large Ignis fatttus in 

 the low marshy grounds, which had the same movements 

 as a Tipula, flying upwards and downwards, backwards 

 and forwards, sometimes as settled and sometimes as if 

 hovering in the air." 



It is remarkable that in this case the wind is de- 

 scribed as being very high, so that a gas or vapour would 

 have been swept onward in a straight line, which was 

 not the case. The insect theory, however, is not free 

 from difficulties. Thus, the question at once arises, Why 

 is this phenomenon so rare ? It may also be asked 

 whether the light given oft" by insects is sufficiently 

 strong to be visible at such distances as the Wisp is said 

 to have been. 



The orthodox theory of the present day — that of spon- 

 taneously inflammable gases, hydrogen phosphide, 

 marsh-gas, and possibly other hydro-carbons given oft" 

 by decomposing animal or vegetable matter — is open to 

 still more formidable objections. The presence of the 

 spontaneously inflammable variety of hydrogen phos- 

 phide has never yet, I believe, been analytically demon- 

 strated among the gaseous matter given oft" from marshes, 

 pools, and graveyards. 



In Brande's "Dictionary of Science, Literature, and 

 Art" (II., p. 191), the Wisp is ascribed to "the issue of 

 marsh-gas from the earth. This gas being ignited either 

 accidentally or intentionally, continues to burn with a 

 flame rufficiently luminous to be well seen at night." 

 The writer adini;s at the same time that no natural pro- 

 duction 01 spontaneously inflammable gas has ever been 

 observed. Now, supposing marsh-gas to be present, 

 how is it to be " accidentally or intentionally " ignited ? 

 Either of these alternatives requires human intervention, 

 exceedingly unlikely in the places where the Wisp has 

 mostly been seen. Dr. Phipson seeks to get over the 

 difficulty of ignition by assuming that the gas given off 

 consists of marsh-gas, through which a small proportion 

 of hydrogen phosphide is dift"used. But an emission of 

 inflammable gases from the earth or the water, however 

 composed and however ignited, will not account for the 

 facts in the majority of cases on record. In proof of this, 

 let any one perform the simple experiment of stirring up 

 the mud at the bottom ofa dirty ditch or pond, and ignite 

 the gas given oft" by means, say, of a piece of taper fixed 

 at the end of a fishing-rod. The gas will burn imme- 

 diately over the surface of the water, but the flame will 

 not travel away for considerable distances — sometimes 

 overleaping hedges, trees or buildings, or playing 

 over thistles, and sometimes remaining stationary 

 for a couple of minutes. It is further found that the 

 Wisp is most common in calm, fine weather, when the 

 barometer is high. But gases pent up in the mud in 



1 marshes, etc, will be most readily liberated when the 



barometer is low. Rainy and windy weather is not 



unfrequently foretokened by the rise of bubbles of gas 



from ponds and marshes. We may readily understand, 



( indeed, that a light produced by inflammable gas might, 



! if the supply was large and constant, hover over an 



I extensive marsh or graveyard. But in such cases it 



I would not be one and the same portion of luminous 



I matter flitting up and down, but a succession of fresh 



I bubbles, jets, or puft's of gas, becoming ignited in turn. 



This accords ill with the facts as reported by observers, 



who generally speak of a single, persisting light. 



Another hypothesis refers the phenomenon to elec- 

 tricity. We often find that the less any person knows 

 about electricity the more ready he is to account for any 

 unexplained facts by its agency. Luminous manifesta- 

 tions of electric nature are certainly well known, such as 

 the " castor and pollux," which appear at the extremities 

 of the masts and yards of ships during stormy weather ; 

 similar lights have been noticed, especially in mountainous 

 regions, attaching themselves to umbrellas, alpenstocks, 

 etc. But these phenomena seem essentially distinct from 

 the true Ignis faiiius which, as it has been said, is 

 characteristic of fine weather, and moves about instead 

 of attaching itself to pointed objects. 



In all probability several distinct phenomena have 

 been confounded under the name of Ignis fatiiits, and 

 careful observation is needed for their respective dis- 

 crimination. Persons who live in or visit regions where 

 the Wisp occurs might do good service by noting all the 

 circumstances of the case at the earliest possible oppor- 

 tunity. The character of the soil, the barometric pres- 

 sure, the temperature, the wind, and, in short, the entire 

 aspect of the weather, should be recorded, and an attempt 

 should be made to take the spectrum of the light, which 

 would be a capital piece of evidence. 



PORTABLE STILL. 



THE annexed woodcut shows the sectional elevation 

 of a little still, designed for the use of photogra- 

 phers, chemists, perfume makers, and others requiring 

 apparatus that shall be at the 

 same time compact, reliable, and 

 economical. The still in ques- 

 tion is entirely free from the 

 complicated and bulky parts of 

 the ordinary " worm" apparatus. 

 J? It consists of a cylinder having 

 as a lid an inverted cone, the 

 apex of which, when fixed in 

 position, rests exactly over a 

 funnel with tube attached passing through the side of 

 the cylinder. To use the still, pour into the cylinder 

 a quantity of tap water and the substance to be dis- 

 tilled, fix on the cone lid, place the whole over a gas 

 stove, spirit lamp, or fire, and permit a gentle stream 

 of cold water to flow in and out of the cone. When 

 the water boils, steam arises, and settling on the lid, is 

 condensed by the cold water outside (which, conse- 

 quently, acts as the refrigerator), ihe purified water runs 

 down the cone into the funnel, whence it passes into the 

 receiving vessel outside. A still, made to distil one 

 gallon of water at each operation, measures less than 

 eighteen inches in height by eight inches diameter, and 

 the manufacturer, C. C. Vevers, Horsforth, Leeds, sup- 

 plies such a machine at 8s. 6d. each. 



