BOOK V

TREATING OF WINDS AND MOVEMENT OF THE ATMOSPHERE

I. Definition of _wind_--air flowing in one direction. The air, like the sea, is always moving, even when it is thought to be still; hence the necessity of the additional qualification--in one direction 193

II. Democritus says wind arises from a multitude of atoms in a small space striving to get free, just like a crowd jostling each other 194

III. But wind does not thus depend on density; cloudy or misty weather does not necessarily produce wind, while wind is produced when the morning sun dissipates the air. Democritus is, therefore, wrong 195

IV. Wind arises in two ways--from the interior of the earth by emission--like wind on the stomach!--and from evaporation 196

V. The air has inherent power of movement, which is the chief cause of wind, evaporation being a less powerful one. Water has the power of moving and of imparting life to animals and plants 197

VI. Fire even, the destroyer, sometimes generates life. Air in like manner has a peculiar power of its own 197

VII. _Breezes before dawn_ arise from rivers, etc. Do not last long 198

VIII. _The “gulf” wind_ (ἐγκολπίας): its origin and duration 198

IX. Connection of winds with seasons of the year and with the heat and light of the sun. The sun does not directly cause the winds 200

X. Some cite the Etesian Winds as proof that he does. They blow in summer when the snows melt and the moisture is carried South 201

XI. But as to the effect of the sun, there is no analogy between the Etesian Winds, which do not spring up till late in the day, and the winds which rise at dawn and fall as the day advances 202

XII. _Cloud squalls_ (ἐκνεφίας). Their formation and combinations 203

XIII. The breaking up of clouds produces wind. Air, in an effort to get free, or heat, may produce this. Interruption of free passage may produce a whirlwind, just as an obstacle in a river a whirlpool. _Violent whirlwinds_ take fire (πρηστήρ). Some winds produce different ones. An analogy holds between air and drops of moisture. A union of forces in air or in dew is necessary to give impulse and produce a current. Air and wind are merely a matter of degree 204

XIV. Mode in which the subterranean winds are generated and make their escape 205

XV. Ancient miners of Philip’s saw rivers and vast underground reservoirs. It is some consolation to read such a story, which shows greed is no new vice: the older generations were as reckless as we are in their quest for treasure better hid 207

XVI. The four _cardinal winds_. The full list includes twelve. Their names and directions 208

XVII. The great circles of the earth which give twelve divisions, and therefore prescribe the possible number of the winds 210

XVIII. The uses of wind and the illustration afforded of the wisdom of Providence. The crops are dependent on it. So is commerce. But we make the sea a highway to war and not to peace. We go to seek for death, as if it were not always near. Xerxes, Alexander, Crassus are warnings of the mischievous use of power to cross the sea. Better, perhaps, the winds had never been given at all. But the value of a natural gift must not be estimated by the depraved use of it. Every gift, even sight and speech, man has perverted in the same way 212