He was the first that found out the nature of light; for, before his day, nobody could tell what the sunshine was composed of.

You remember, I suppose, the story of an apple's falling on his head, and thus leading him to discover the force of gravitation, which keeps the heavenly bodies in their courses.

When he had once got hold of this idea, he never permitted his mind to rest until he had searched out all the laws by which the planets are guided through the sky.

This he did as thoroughly as if he had gone up among the stars and tracked them in their orbits.

The boy had found out the mechanism of a windmill; the man explained to his fellow-men the mechanism of the universe.
While making these researches he was accustomed to spend night after night in a lofty tower, gazing at the heavenly bodies through a telescope.