His discoveries in optics were in his own time almost equally famous,
while in his later life he shared with Leibnitz the honor of inventing
the infinitesimal calculus, a method which lies at the root of all the
intricate marvels of modern mathematical science.

Newton should not, however, be regarded as an isolated phenomenon, a genius
but for whom the world would have remained in darkness. His first flashing
idea of gravitation deserves perhaps to be called an inspiration. But in
all his other labors, experimental as well as mathematical, he was but
following the spirit of the times. The love of science was abroad, and its
infinite curiosity. Each of Newton's discoveries was claimed also by other
men who had been working along similar lines. Of the dispute over the
gravitation theory Sir David Brewster, the great authority for the career
of Newton, gives some account. The controversy over the calculus was even
more bitter and prolonged.

It were well, however, to disabuse one's mind of the idea that Newton's
work was a finality, that it settled anything. As to why the law of
gravitation exists, why bodies tend to come together, the philosopher had
little suggestion to offer, and the present generation knows no more than
he. Before Copernicus and Newton men looked only with their eyes, and
accepted the apparent movements of sun and stars as real. Now, going one
step deeper, we look with our brains and see their real movements which
underlie appearances. Newton supplied us with the law and rate of the
movement--but not its cause. It is toward that cause, that great "Why?"
that science has ever since been dimly groping.

In the year 1666, when the plague had driven Newton from Cambridge, he was
sitting alone in the garden at Woolsthrope, and reflecting on the nature of
gravity, that remarkable power which causes all bodies to descend toward