LVII
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What do I think myself about the matter, you ask. For up to this point I have been reproducing the opinions of others. Well, I will tell you. There is lightning when light bursts out suddenly and widely. This occurs when the atmosphere has been changed, by the rarefaction of the clouds, into fire, which has not gathered strength to issue to any considerable distance. There is, I presume, no cause for surprise either that movement rarefies air or that rarefaction kindles fire. In the same way a leaden bullet is liquefied when discharged from a sling, and falls in drops by reason of atmospheric friction just as it would do through fire. Bolts of lightning are more numerous in summer, for the reason that there is most heat at that season. Fire naturally starts more readily when the friction is in warmer air. A flash of lightning which merely gleams and a bolt which is discharged are produced in exactly the same way. But there is less force in the former case and less fuel. To put my opinion on the point shortly: a bolt is just lightning in its most intense form. So then, when a body of the nature of heat or smoke is exhaled from the earth and, meeting with clouds, is for a long time rolled about in their hollows, at last it bursts out. Since it possesses no strength, it is merely a flash. But when lightnings have more material and burn with fiercer glow, they not merely become visible, but also fall to the earth.