Before, however, he could start out, as he had promised, to conquer Persia, he was killed by one of his own men, so that he was unable to carry out his plan.

But Philip had a son named Alexander. Alexander was only twenty years old, not old enough even to vote if he had lived in our country, but when his father died he became king of Macedonia and also of Greece.

When Alexander was a mere child, he saw some men trying without success to tame a young and very wild horse that shied and reared in the air so that no one was able to ride it. Alexander asked to be allowed to try to ride the animal. Alexander’s father made fun of his son for wanting to attempt what those older than he had been unable to do, but at last gave his consent.

Now, Alexander had noticed what the others, although much older, had not noticed. The horse seemed to be afraid of its own shadow, for young colts are easily frightened by anything black and moving, as some children are afraid of the dark.

So Alexander turned the horse around facing the sun, so that its shadow would be behind, out of sight. He then mounted the animal and, to the amazement of all, rode off without any further trouble.

His father was delighted at his son’s cleverness and gave him the horse as a reward. Alexander named the horse Bucephalus and became so fond of him that when the horse died Alexander built a monument to him and named several cities after him.

Now, Alexander was a wonderful boy, but he had such a wonderful teacher named Aristotle that some people think part, at least, of his greatness was due to the teacher.

Aristotle was probably the greatest teacher that ever lived. If there were more great teachers like Aristotle, it seems likely there would have been more great pupils like Alexander.

Aristotle wrote books about all sorts of things—books about the stars called astronomy, books about animals called zoölogy, and books on other subjects that you probably have never even heard of, such as psychology and politics.

For thousands of years these books that Aristotle wrote were the school-books that boys and girls studied, and for a thousand years they were the only school-books. Nowadays, a school-book is usually old-fashioned a few years after it is written and is then no longer used. So you see how remarkable it was that Aristotle’s school-books should have been used for so long a time.