It is certain that the lightning is seen before the thunder is heard, although they both take place at the same time. Nor is this wonderful, since light has a greater velocity than sound. Nature so regulates it, that the stroke and the sound coincide[412]; the sound is, however, produced by the discharge of the thunder, not by its stroke. But the air is impelled quicker than the lightning[413], on which account it is that everything is shaken and blown up before it is struck, and that a person is never injured when he has seen the lightning and heard the thunder. Thunder on the left hand is supposed to be lucky, because the east is on the left side of the heavens[414]. We do not regard so much the mode in which it comes to us, as that in which it leaves us, whether the fire rebounds after the stroke, or whether the current of air returns when the operation is concluded and the fire is consumed. In relation to this object the Etrurians have divided the heavens into sixteen parts[415]. The first great division is from north to east; the second to the south; the third to the west, and the fourth occupies what remains from west to north. Each of these has been subdivided into four parts, of which the eight on the east have been called the left, and those on the west the right divisions. Those which extend from the west to the north have been considered the most unpropitious. It becomes therefore very important to ascertain from what quarter the thunder proceeds, and in what direction it falls. It is considered a very favourable omen when it returns into the eastern divisions. But it prognosticates the greatest felicity when the thunder proceeds from the first-mentioned part of the heavens and falls back into it; it was an omen of this kind which, as we have heard, was given to Sylla, the Dictator. The remaining quarters of the heavens are less propitious, and also less to be dreaded. There are some kinds of thunder which it is not thought right to speak of, or even to listen to, unless when they have been disclosed to the master of a family or to a parent. But the futility of this observation was detected when the temple of Juno was struck at Rome, during the consulship of Scaurus, he who was afterwards the Prince of the Senate[416].