THE ORDER OF THE FIRST BOOK ON WATER.

Define first what is meant by height and depth; also how the
elements are situated one inside another. Then, what is meant by
solid weight and by liquid weight; but first what weight and
lightness are in themselves. Then describe why water moves, and why
its motion ceases; then why it becomes slower or more rapid; besides
this, how it always falls, being in contact with the air but lower
than the air. And how water rises in the air by means of the heat of
the sun, and then falls again in rain; again, why water springs
forth from the tops of mountains; and if the water of any spring
higher than the ocean can pour forth water higher than the surface
of that ocean. And how all the water that returns to the ocean is
higher than the sphere of waters. And how the waters of the
equatorial seas are higher than the waters of the North, and higher
beneath the body of the sun than in any part of the equatorial
circle; for experiment shows that under the heat of a burning brand
the water near the brand boils, and the water surrounding this
ebullition always sinks with a circular eddy. And how the waters of
the North are lower than the other seas, and more so as they become
colder, until they are converted into ice.

Definitions (931. 932).