CHAPTER	PAGE
LVI.	Heraclitus and Caecina consider sheet lightning to be intermittent, incipient fire. Changes in the pronunciation of the Latin word.
LVII.	Lightning is likely due to the air turning into fire through the thinning (rarefaction) of clouds. It is naturally most frequent in summer. Sheet and forked lightning differ in degree, not in kind.
LVIII.	Reasons for the rapidity of lightning and its zigzag path.
LIX.	Every story should have a moral. Death cannot be prevented; why fear it? It is cowardly and foolish. Death by lightning is an honor rather than otherwise. Besides, fear is futile.

BOOK III

ON FORMS OF WATER

PREFACE


Having begun a mighty task in my old age, I must make up for lost time by hurrying. The magnitude of the task is actually an incentive to effort. Such studies are far superior to the historian’s task of recording the deeds of the robbers and butchers of mankind. The former raise us above the changes of fortune. "The principal thing" is to have a pure heart and clean hands, to escape slavery to self. The study of the universe exalts us to this.	109
I.	The cause of rivers and their varieties. Waters vary in volume by season, in temperature, and in medicinal qualities.
II.	Varieties of taste, weight, color, health benefits, and consistency.
III.	Gravitation or the force of air determines the flow of water. Surface water and spring water may be combined, as in Lake Fucinus.
IV.	Why is the sea not filled, nor the earth drained dry, by rivers?
V.	Some hold that what flows into the sea returns through secret passages, cleansed of its salinity.
VI.	Some believe rain supplies the rivers, citing the interior of Africa as contrasted with Gaul and Germany.
VII.	Objections to this argument: Rain does not penetrate more than 10 feet. If the earth is dry, it absorbs the rain; if it is saturated, the rain runs off. Furthermore, rivers rise in rocks and mountains, where any rain that fell must have immediately run off. Rich wells of "living" water are found in the driest ground at great depths. Fountains spring forth at mountain tops.
VIII.	The interior of the earth is, according to some, a huge reservoir of fresh water.
IX.	Others think that air contained within the earth, being prevented from circulating, turns into water.
X.	In truth, the four elements are all interchangeable.
XI.	Although the supply of water is perennial, rivers and springs are intermittent.
XII.	The abundance of water is not a problem, as it constitutes a fourth part of the universe.