A few years since the inhabitants of Southboro', Massachusetts, were excited and alarmed at the appearance of a light, about the size of a star, which for several successive nights was seen moving over a spot of land in the westerly part of the town. Upon examining the premises by daylight, it was found that a quantity of bones that had been buried in the earth had been thrown upon the surface by the roots of a tree, the trunk of which had recently been prostrated by a gale of wind. By many, these bones were supposed to belong to some human being, who, it was conjectured, had been murdered, and buried beneath the spot. And the light seen hovering near was considered indicative of such an event. But if the reader will turn to the second chapter of this work, he will learn that these dancing lights, so called, arise from an inflammable gas, evolved from decayed animal and vegetable substances, which take fire on coming in contact with atmospheric air. This ignis fatuus, Jack-with-a-lantern, or Will-with-a-wisp appearance is generally seen in dark nights, over boggy and marshy ground, and generally in motion, at the height of five or six feet, skipping from place to place, and frequently changing in magnitude and form. On some occasions, it is observed to be suddenly extinguished, and then to reappear at a distance from its former position. Those persons who have endeavored to examine it closely have found that it moves away from them with a velocity proportioned to that of their advance—a circumstance which has had no small influence on the fears of the ignorant and superstitious. Dr. Denham once saw an ignis fatuus in a boggy place, between two rocky hills, in a dark and calm night. He approached by degrees within two or three yards of it, and thereby had an opportunity of viewing it to the best advantage. It kept skipping about a dead thistle, till a slight motion of the air—occasioned, as he supposed, by his near approach—caused it to jump to another place; and as he advanced it kept flying before him. He observed it to be a uniform body of light, and concluded it must consist of ignited vapor. These appearances are common on the plains of Boulogne, in Italy, where they sometimes flit before the traveller on the road, saving him the expense of a torch on dark nights. Sometimes they spread very wide, and then contract themselves; and sometimes they float like waves, and appear to drop sparks of fire. They shine more strongly in rainy than in dry weather.

An appearance of the same kind is sometimes met with at sea, during gales of wind, and, of course, has become connected with many superstitious notions of sailors, who call it a corpusant. There are sometimes two together, and these are named Castor and Pollux. The following is a description of one, given by the voyager Dampier: "After four o'clock the thunder and the rain abated, and then we saw a corpusant, at our maintopmast head. This sight rejoiced our men exceedingly, for the height of the storm is commonly over when the corpusant is seen aloft; but when they are seen lying on the deck, it is generally accounted a bad sign. A corpusant is a certain small, glittering light; when it appears, as this did, on the very top of a mainmast, or at a yardarm, it is like a star; but when it appears on the deck, it resembles a great glowworm. I have been told that when the Spanish or Portuguese see them they go to prayers, and bless themselves for the happy sight. I have heard some ignorant seamen discoursing how they have seen them creep, or, as they say, travel about, in the scuppers, telling many dismal stories that happened at such times; but I did never see any one stir out of the place where it was first fixed, except on deck, where every sea washeth it about. Neither did I ever see any but when we had rain as well as wind, and, therefore, do believe it is some jelly."

The origin and nature of the lights above described have not yet been satisfactorily explained. More accurate observations than have been made are required to furnish the basis of a correct theory respecting them.