Page:Early Greek philosophy by John Burnet, 3rd edition, 1920.djvu/251

Rh The first of the elements to be separated out by Strife then, was Air, which took the outermost position surrounding the world (cf. fr. 38). We must not, however, take the statement that it surrounded the world "in a circle" too strictly. It appears that Empedokles regarded the heavens as shaped like an egg. Here, probably, we have a trace of Orphic ideas. At any rate, the outer circle of the Air became solidified or frozen, and we thus get a crystalline vault as the boundary of the world. We note that it was Fire which solidified the Air and turned it to ice. Fire in general had a solidifying power.

In its upward rush Fire displaced a portion of the Air in the upper half of the concave sphere formed by the frozen sky. This air then sunk downwards, carrying with it a small portion of the fire. In this way, two hemispheres were produced: one, consisting entirely of fire, the diurnal hemisphere; the other, the nocturnal, consisting of air with a little fire.

The accumulation of Fire in the upper hemisphere disturbs the equilibrium of the heavens and causes them to revolve; and this revolution not only produces the alternation of day and night, but by its rapidity keeps the heavens and the earth in their places. This was illustrated, Aristotle tells us, by the simile of a cup of water whirled round at the end of a string. This experimental illustration is much in the manner of Empedokles. It has nothing to do with "centrifugal force," but is intended to show that rapid motion may counteract a tendency to fall.

113. It will be observed that day and night have been explained without reference to the sun. Day is the light