The abo%e hypothesis, fanciful as it may appear, and inadequate as it unquestionably is to account for all the phenomena of meteors, points to a plausible explana tion of another luminous appearance, the cause of which has not yet been ascertained, and which, though differing in many respects from the bodies above de scribed, bears a sufficiently close resemblance to them, to be classed under the general head of meteors. \Ve allude to the well known light called Ignis Fatuus, Jack with a lantern, or Will with the wisp, so named from the superstitious notions which have been attach ed to its appearance. It is generally seen in dark nights, over boggy and marshy ground, sometimes at rest on the surface, but generally in motion at the height of five or six feet, skipping from place to place, and frequently changing both in magnitude and form. On some occasions it is observed to be suddenly extin guished, and afterwards to reappear at a distance from its former position. Those who have endeavoured to examine it more closely, or who have been accidentally led to approach it, generally remark that it moves away from them, and with a velocity proportional to that with which they advance, a circumstance which has had no small influence on the fears of the ignorant and superstitious. A particular account of the ignis fatuus, as seen on two different occasions, will be found in Cavallo's Elements of Natural Philosophy, Vol. III. p. 329.
To apply the above hypothesis to the explanation of this phenomenon, let us suppose that some such phos phoric fluid a., that mentioned by D Luc, arising from the decomposition of animal or vegetable substances, passes into the atmosphere, and continues to float there without mixing with the atmosphere itself, or being dissipated by the wind. We can then conceive that this fluid, having become luminous by some sort of ig nition, at the place where it is least affected by the in termixture of moisture or other substances, successive ly communicates with other portions of itself, so long as the column continues unbroken. In this way the luminous body will move from place to place, following the direction which the fluid had previously taken, and it will appear more or less brilliant, according to the quantity or purity in which the fluid exists at any given point. The occasional disappearance of the light may be owing to an interruption in the column, or to the quantity of phosphoric matter being so small as not to be visible till the ignition arrive at another puint, where the inflammable matter is more abundant, and consequently reappears. We could anticipate many difficulties and objections to this explanation, which we doubt not will readily occur to our readers. But though we are not aware of any which might not ad mit of a plausible refutation, enough has been said on a subject that requires numerous and more accurate ob servations than any that have yet been made, to furnish the basis of a satisfactory theory.
Besides the meteors already described, there are other luminous appearances occasionally observed in the at mosphere, which belong also to the first class of prog nostics, viz. Halos, Parhelia, or Mock Suns, I'ara
selenia, or Mock Moons, and the Rainbow. The in vestigation of these phenomena properly belongs to Op tics, and to that article we refer for an account of such of them as have not already been described in the course of this work. (See HALO.) We notice them here, only because they are supposed to indicate certain approach ing changes in the state of the weather. The lumi nous circle which is sometimes seen around the hea venly bodies, but especially the sun or moon, and which has received the name of Halo, or Corona, has, from a very early period, been regarded as a certain prognostication of stormy weather, accompanied with rain or snow, according to the climate or season of the year. It frequently happens, that, in the outer edge, or circumference of this circle, there is a part less dis tinctly defined than the rest, apparently owing to the contact of a denser cloud; and it has been remarked by shepherds and others, who have frequent opportu nities of observing this phenomenon, that the storm ge nerally comes from that point of the compass, towards which this indistinct portion of the circle, or opening as it is called, was directed. If there is any founda tion for this remark, it may perhaps he accounted for on the principle already stated, regarding the change of wind in the higher and lower regions of the atmos phere. The current that is to bring the approaching storm may have set in above, before the halo disap pears, and by accumulating the clouds upon it from that quarter, produce the indistinctness alluded to. This phenomenon, as well as its modifications the Par helion and Paraselene, is obviously connected with a change of weather, only in so far as it indicates some peculiarity in the state of the atmosphere. The same remark applies to the rainbow, though this last is ra ther a concomitant, than a prognostication of rain. It has been remarked, however, that a rainbow in the morning is frequently followed by showers, while one in the evening forebodes fair weather.
It has been a long established, and generally receiv ed opinion, that the phases of the moon have a cer tain influence nn the weather, and these have accord ingly furnished various prognostications, which may also be referred to the first class. It is quite conceiv able, on philosophical principles, that the atmosph zre may be differently affected, in the same way as the waters of the ocean arc, by the different positions (li the sun and moon, telatively to tha earth ; and the result in certain cases, may be a tract of settled or tempestuous weather, according to circumstances. At the same time the subject is still involved in great tn. certainty ; nor does there appear to be any foundation for the common opinion, that if the new or full moon happens about midnight, dry weather will follow ; Lut if it takes place about noon, rain may be expected. The rule does no doubt hold in many instances ; but on looking over our observations for a series of years, we find that it also frequently fails.