The first is red, the second orange, the third yellow, the fourth green, the fifth blue, the sixth indigo, the seventh a violet purple.

Each of these rays transmitted afterwards by a hundred other prisms will never change the color it bears; in like manner as gold, when completely purged from its dross, will never change afterwards in the crucible."(3) XII.

NEWTON AND THE LAW OF GRAVITATION We come now to the story of what is by common consent the greatest of scientific achievements.

The law of universal gravitation is the most far-reaching principle as yet discovered.

It has application equally to the minutest particle of matter and to the most distant suns in the universe, yet it is amazing in its very simplicity.