The notion of Descartes entirely belongs to Aristotle, who says, that “thunder is caused by a dry exhalation, which, falling upon a humid cloud, and violently endeavouring to force a passage for itself, produces the peals which we hear.” Anaxagoras refers it to the same cause.
All the other passages, which occur in such abundance among the ancients, respecting thunder, contain in them the reasonings of the Newtonians, sometimes combining the notions of Descartes.
Leucippus, and the Eleatic sect, held that “thunder proceeded from a fiery exhalation, which, enclosed in a cloud, burst it asunder, and forced its way through.” Democritus asserts, that it is the effect of a mingled collection of various volatile particles, which impel downwards the cloud which contains them, till, by the rapidity of their motion, they set themselves and it on fire.
Seneca ascribes it to a dry sulphureous exhalation arising out of the earth, which he calls the aliment of lightning; and which, becoming more and more subtilized in its ascent, at last takes fire in the air, and produces a violent eruption.
According to the stoics, thunder was occasioned by the shock of clouds; and lightning was the combustion of the volatile parts of the cloud, set on fire by the shock. Chrysippus taught, that lightning was the result of clouds being set on fire by winds, which dashed them one against another; and that thunder was the noise produced by that rencontre: he added, that these effects were coincident; our perception of the lightning before the thunder-clap being entirely owing to our sight’s being quicker than our hearing.
In short, Aristophanes, in his comedy of the “Clouds,” introducing Socrates as satisfying the curiosity of one of his disciples as to the cause of thunder, makes him assign it to the action of the compressed air in a cloud, which dilating itself bursts it, and, violently agitating the exterior air, sets itself on fire, and by the rapidity of its progress occasions all that noise.
The Aurora Borealis was also observed by the ancients, as may be seen in Aristotle, Pliny, Seneca, and other writers, who conjectured differently its cause.
The Cartesians, Newtonians, and other able moderns, ascribe Earthquakes to the earth’s being filled with cavities of a vast extent, containing in them an immense quantity of thick exhalations, resembling the smoke of an extinguished candle, which being easily inflammable, and by their agitation catching fire, rarefy and heat the central and condensed air of the cavern to such a degree, that finding no vent, it bursts its enclosements; and, in doing this, shakes the surrounding earth all around with dreadful percussions, producing all the other effects which naturally follow.
Aristotle and Seneca assigned these dreadful events to the same cause. The former says, that they were occasioned by the efforts of the internal air in dislodging itself from the bowels of the earth; and he observes, that on the approach of an earthquake the weather is generally serene, because that sort of air which occasions commotions in the atmosphere, is at that time pent up in the entrails of the earth.
Seneca is so precise, we might take him for a naturalist of the present times. He supposes that the earth hides in its bosom many subterraneous fires, which uniting their flames, necessarily put into fervid motion the congregated vapours of its cells, which finding no immediate outlet, exert their utmost powers, till they force a way through whatever opposes them. He says also, that if the vapours be too weak to burst the barriers which retain them, all their efforts end in weak shocks, and hollow murmurs, without any fatal consequence.