The distribution of thunderstorms is as yet not well understood, but it appears in many cases that they are attendants on the advancing face of cyclones and hurricanes, the area in front of these great whirlstorms being subjected to the condensation and irregular air movements which lead to the development of much electrical energy. There are, however, certain parts of the earth which are particularly subjected to lightning flashes. They are common in the region near the equator, where the ascending currents bring about heavy rains, which mean a rapid condensation and consequent liberation of electrical energy. They diminish in frequency toward the arctic regions. An observer at the pole would probably fail ever to perceive strong flashes. For the same reason thunderstorms are more frequent in summer, the time when the difference in temperature between the surface and the upper air is greatest, when, therefore, the uprushes of air are likely to be most violent. They appear to be more common in the night than in the daytime, for the reason that condensation is favoured by the cooling which occurs in the dark half of the day. It is rare, indeed, that a thunderstorm occurs near midday, a period when the air is in most cases taking up moisture on account of the swiftly increasing heat. There are other forms of electrical discharges not distinctly connected with the then existing condensation of moisture. What the sailors call St. Elmo's fire--a brush of electric light from the mast tops and other projections of the ship--indicates the passage of electrical energy between the vessel and the atmosphere. Similar lights are said sometimes to be seen rising from the surface of the water. Such phenomena are at present not satisfactorily explained. Perhaps in the same group of actions comes the so-called "Jack-o'-lantern" or "Will-o'-the-wisp" fires flashing from the earth in marshy places, which are often described by the common people, but have never been observed by a naturalist. If this class of illuminations really exists, we have to afford them some other explanation than that they are emanations of self-inflamed phosphoretted hydrogen, a method of accounting for them which illogically finds a place in many treatises on atmospheric phenomena. A gas of any kind would disperse itself in the air; it could not dance about as these lights are said to do, and there is no chemical means known whereby it could be produced in sufficient purity and quantity from the earth to produce the effects which are described.[3]