Meteorology

he thought that the upper regions were full of fire, and that men referred to those regions when they spoke of
25 ether the shining or upper sky. In the latter point he was right, for men seem to have assumed that a body that was eternally in motion was also divine in nature; and, as such a body was different from any of the terrestrial elements, they determined to call it ‘ether’.

For the same opinions appear in cycles among men not once nor twice, but infinitely often.
30 Now there are some who maintain that not only the bodies in motion but that which contains them is pure fire, and the interval between the earth and the stars air : but if they had considered what is now satisfactorily established by mathematics, they might have given up this puerile opinion. For it is altogether childish to suppose that the
35 moving bodies are all of them of a small size, because they seem so to us, looking at them from the earth.

This is a matter which we have already discussed in our treatment of the upper region, but we may return to the point now.
340^a If the intervals were full of fire and the bodies consisted of fire every one of the other elements would long ago have vanished.

However, they cannot simply be said to be full of air either; for even if there were two elements to fill the space between the earth and the heavens, the air would far exceed the quantity required to maintain its proper proportion to
5 the other elements. For the bulk of the earth (which includes the whole volume of water) is infinitesimal in comparison with the whole world that surrounds it. Now we find that the excess in volume is not proportionately
10 great where water dissolves into air or air into fire. Whereas the proportion between any given small quantity of water and the air that is generated from it ought to hold good between the total amount of air and the total amount of water. Nor does it make any difference if any one denies
that the elements originate from one another, but asserts that they are equal in power.