When their young begin to be able to use their wings, they attend and instruct them; and then their cares are at an end.
Human art and industry are indeed necessary towards the preservation and improvement of certain animals and vegetables; for there are several of both kinds which would perish without that assistance.

There are likewise innumerable facilities (being different in different places) supplied to man to aid him in his civilization, and in procuring abundantly what he requires.

The Nile waters Egypt, and after having overflowed and covered it the whole summer, it retires, and leaves the fields softened and manured for the reception of seed.

The Euphrates fertilizes Mesopotamia, into which, as we may say, it carries yearly new fields.[228] The Indus, which is the largest of all rivers,[229] not only improves and cultivates the ground, but sows it also; for it is said to carry with it a great quantity of grain.

I could mention many other countries remarkable for something singular, and many fields, which are, in their own natures, exceedingly fertile.
LIII.