Chap. 43.] OF THUNDER AND LIGHTNING. 69 are the Suculre ; there is also Bootes, which follows the seven northern stars ^ CHAP. 42. (42.) — OF UNCERTAIN STATES OF THE WEATHEB. But I would not deny, that there may exist showers and winds, independent of these causes, since it is certain that an exhalation proceeds from the earth, which is sometimes moist, and at other times, in consequence of the vapours, like dense smoke ; and also, that clouds are formed, either from the fluid rising up on high, or from the air being com- pressed into a fluid'-^. Their density and their substance is very clearly proved from their intercepting the sun's rays, which are visible by divers, even in the deepest waters^. CHAP. 43. (43.) — OF THUNDER AND LIGHTNING. It cannot therefore be denied, that fire proceeding from the stars which are above the clouds, may fall on them, as we frequently observe on serene evenings, and that the air is agitated by the impulse, as darts when they are hurled whiz through the air. And when it arrives at the cloud, a dis- cordant kind of vapour is produced, as when hot iron is plunged into water, and a wreath of smoke is evolved. Hence arise squalls. And if wind or vapour be struggling in the cloud, thunder is discharged ; if it bursts out with a flame, there is a thunderbolt ; if it be long in forcing out its way, it is simply a flash of lightning'*. By the latter the cloud is simply rent, by the former it is shattered. Thunder is pro- 1 " Septemtriones." 2 The doctrine of Aristotle on the nature and formation of mists and clouds is contained in his treatises De Meteor, hb. i. cap. 9. p. 540, and De Mundo, cap. 4. p. 605. He employs the terms dryitJs, r-e^os, and ve^eXjj, which are translated vapor, nuhes and nebula, respectively. The distinction, however, between the two latter does not appear vexy clearly marked either in the Greek or the Latin, the two Greek words be^g in- discriminately applied to either of the Latin terms. 3 It is doubthil how far this statement is correct ; see the remarks of Hardouin, Lem. i. 320. ^ The words in the original are respectively fiilmen and fulgetrum ; Seneca makes a similar distinction heivfccn fulmen and fiilgu ratio : " Ful- guratio est late ignis exphcitus ; fulmen est coactus ignis ot impetu jactus." Nat. Quaest. Ub. ii. cap. 16. p. 706.
