The meteors known to the ancients were called [Greek: Lampdes Pithoi] Bolides, Faces, Globi, etc. from particular differences in their shape and appearance, and sometimes under the general term of comets. In the Philosophical Transactions, they are called, indiscriminately, fire-balls, or fiery meteors; and names of similar import have been applied to them in the different languages of Europe. The most material circumstances observed of such meteors may be brought under the following heads: 1. Their general appearance. 2. Their path. 3. Their shape or figure. 4. Their light and colour. 5. Their height. 6. The noise with which they are accompanied. 7. Their fire. 8. Duration, 9. Their velocity. Under these different heads meteors have been investigated by the scrutinizing of philosophy, and many superstitious notions, long entertained concerning them, entirely exploded. Meteoric phenomena, it has been demonstrated, all proceed from one common cause--irregularity in the density of the atmosphere. When the atmospheric fluid is homogenous and of equal density, the rays of light pass without obstruction or alteration in their shape or direction; but when they enter from a rarer into a denser medium, they are refracted or bent out of their course; and this with greater or less effect according to the different degrees of density in the media, or the deviation of the ray from the perpendicular. If the second medium be very dense in proportion, the ray will be both refracted and reflected; and the object from which it proceeds, will assume a variety of grotesque and extraordinary shapes, and it will sometimes appear as in a reflection from a concave mirror, dilated in size, and changed in situation. The following striking effects are known to proceed from this simple cause.