Tempests, and bright lightnings, are to be sung; their nature is to be told, and from what cause they pursue their course; lest, having foolishly divided the heaven into parts, you should be anxious as to the quarter from which the flying flame may come, or to what region it may betake itself; and tremble to think how it penetrates through walled enclosures, and how, having exercised its power, it extricates itself from them. Of which phenomena the multitude can by no means see the causes, and think that they are accomplished by supernatural power.