Thunder and Lightning

by Camille Flammarion

Who knows whether, later on, when phonography is brought to perfection, it will not also register the noisy accompaniment to the electric flash? Then, with the help of the cinematograph, we could have dramatic representations of sensational storms. While the photograph unrolls all the phases of the lightning, from its emerging from the cloud to its fall to earth, before the gaze of the spectators, the phonograph will repeat the sonorous accents of the terrorizing voice of thunder.

Thunder, as all the world knows, is the noise which accompanies lightning. It is produced when a change of electricity—a neutralization—takes place between two points more or less distant. The causes which provoke it are still somewhat of a mystery.

The luminous rocket which flings itself precipitately from a cloud saturated with electricity, spreads itself like a trail of flames in the atmosphere where an infinity of invisible molecules are floating; these it repels. The passage of this whirlwind of fire in a centre which is greatly compressed produces a momentary void into which the surrounding air at once rushes, and it is the same all the way along the route followed by lightning.

In all probability the equilibrium of the atmosphere, which is momentarily disturbed by the intrusion of the ignited matter, hastily re-establishes itself by a rush of the air which the lightning has ejected, and which is swallowed up with a crash in the opening which has been made. It is, on a large scale, a similar phenomenon to that which is produced by opening a case which has been hermetically sealed. The air rushing in makes a dull noise.

Pouillet objects to this very natural explanation on the ground that the flight of a cannon-ball ought to produce a similar noise. But this objection errs in its basis, because, as regards velocity, a cannon-ball is as a tortoise as compared with the arrow of lightning, and as regards size, who can compare a few grammes of powder to the torrents of fire launched into space by the prodigious force of electricity?

The lightning discharge produces a violent concussion in the cloud, and very often a shower of rain immediately follows it. The electric conditions of the different clouds which make a storm being separately liable the one to the other, the discharge of one must lead to that of several others more or less distant. In all cases the noise is caused by the expansion of the air where a more or less partial void has been made. It is the same with firearms, crève-vessie, etc.

One of the chief characteristics of thunder is the rolling, which is often prolonged, and reverberates on the sides of steep mountains. This voice, with its lugubrious tone, becomes grave and sometimes sinister in the revolution of space—this voice, celestial and infernal, seems to momentarily dominate the world, while the clouds are enveloped with a thousand diabolical flames. Sometimes it rings in the air with fierce calls, at others it spreads itself in dull, languorous complaints.

Nevertheless, the intenseness of thunder undergoes a thousand fluctuations, and presents astonishing variations. Generally it strikes and frightens, but the curious thing is that, for the ear, in reality it is less strong than the crinkling noise of a piece of paper torn close to it.

Often, too, it may be compared to the discharge of firearms, a pistol or a cannon.

Thus, when the lightning penetrated Volney's apartments at Naples, the people present, among whom was Saussure, had the impression of a pistol-shot in the next room.