XXVIII. In order to the sound of thunder, clouds of a particular shape must meet in a particular way. A bladder does not burst with a report if cut. A broad simultaneous blow over the whole cloud is necessary to an explosion 76 XXIX. The proper shape and the rupture of the cloud are necessary. Compare drums, etc. 77 XXX. According to some, clouds are not necessary to thunder: witness eruptions of Etna and the overthrow of Cambyses’ army, where particles of sand were the medium of the thunder and lightning. But in this case, too, a cloud was formed, it may be, a denser, and more solid than one composed of mere air, before the sound was emitted 77 XXXI. Strange effects of lightning 78 XXXII. Portents and events, their undoubted and widespread connection 79 XXXIII. Thunderbolts. Threefold division of the art of dealing with them 81 XXXIV. Mistaken views as to the relation of lightning to other presages. The former are of equal, not superior, value 82 XXXV. Fate cannot be changed by expiation and entreaty 83 XXXVI. “God is not a man” that he should change fate. What is the use, then, of rites? 84 XXXVII. Answer--Fate fixes some things only conditionally: the alternative issues are determined by the conduct, active or passive, of the worshipper 84 XXXVIII. This action of his is likewise a part of fate. The soothsayer, like the physician, is the minister of fate. Discussion of free will deferred 85 XXXIX. Three classes or kinds of thunderbolts, as judged by their indications, according to Caecina 86 XL. These are kinds of prognostications rather than of bolts. The different species of the latter are distinguished by their effects--boring, splitting, burning. Fine distinctions of Latin terms 87 XLI. A kind that stains or discolours. The Etruscan view of the three kinds of bolt according to _their_ division 88 XLII. The Etruscans knew what they were about in attributing certain motives and actions to Jupiter. Their theory was for the benefit of the ignorant mass of humanity 89 XLIII. “Which things are an allegory.” An example is set to earthly rulers to be merciful and consider well their judgments 90 XLIV. Jove does not change his missiles; but there are gradations in the offence to be punished. That is the lesson 91