rise higher than the point from which it falls, he reached
correct conclusions as to the general principle of the conservation of
vis viva, although he did not actually prove his conclusions. This was
the first attempt to deal with the dynamics of a system. In this work,
also, was the true determination of the relation between the length of a
pendulum and the time of its oscillation.

In 1681 he returned to Holland, influenced, it is believed, by the
attitude that was being taken in France against his religion. Here he
continued his investigations, built his immense telescopes, and, among
other things, discovered "polarization," which is recorded in Traite
de la Lumiere, published at Leyden in 1690. Five years later he
died, bequeathing his manuscripts to the University of Leyden. It
is interesting to note that he never accepted Newton's theory of
gravitation as a universal property of matter.

XI. NEWTON AND THE COMPOSITION OF LIGHT

Galileo, that giant in physical science of the early seventeenth
century, died in 1642. On Christmas day of the same year there was born
in England another intellectual giant who was destined to carry forward
the work of Copernicus, Kepler, and Galileo to a marvellous consummation
through the discovery of the great unifying law in accordance with
which the planetary motions are performed. We refer, of course, to the
greatest of English physical scientists, Isaac Newton, the Shakespeare
of the scientific world. Born thus before the middle of the seventeenth
century, Newton lived beyond the first quarter of the eighteenth
(1727). For the last forty years of that period his was the dominating
scientific personality of the world. With full propriety that time has
been spoken of as the "Age of Newton."

Yet the man who was to achieve such distinction gave no early
premonition of future greatness. He was a sickly child from birth, and
a boy of little seeming promise. He was an indifferent student, yet, on
the other hand, he cared little for the common amusements of boyhood. He
early exhibited, however, a taste for mechanical contrivances, and spent
much time in devising windmills, water-clocks, sun-dials, and kites.
While other boys were interested only in having kites that would
fly, Newton--at least so the stories of a later time would have us
understand--cared more for the investigation of the seeming principles
involved, or for testing the best methods of attaching the strings, or