The fluid, or gas, which fills the mid-plane and intermediate cavities, is most probably the same, or partaking of the same nature, (though perhaps in a purer state,) with that which oozes out of fissures in the earth, at the bottom of deep mines, called by chemists, _hydro-carbonate_; which being highly inflammable, takes fire from the lamps used by workmen, and explodes with such violence as to destroy both men and horses employed in the mine. This is a frequent occurrence in the deep coal mines of England; and great numbers annually have lost their lives in this way, before the introduction of Sir Humphrey Davy's lamp. I am also informed, from good authority, that the miners, in some of the deep coal mines in England, once felt, or heard an earthquake, which happened in Italy, whilst those on the surface of the ground had no knowledge of it. This would be the case, if the intermediate cavity, which caused the earthquake, extended in that direction, and near the bottom of the mine; as it is presumed the rare gas with which those spaces are filled, is better adapted to the conveyance of sound, or vibratory motion, than the more solid parts of the sphere, or even the atmosphere around us. On the supposition that the globe is solid, and the matter composing it at rest, as respects itself, on what principle can boiling and hot springs be accounted for; some of which issue out several thousands of miles distant from where any volcano or subterranean fire is known to exist; particularly as to those on the waters of Red river, in the state of Louisiana, which are sufficiently hot to cook meat in a few minutes.