In view of this state of things it must be regarded as one of the
most remarkable facts in evolutionary history that four or five
men, whose mental constitution was either typical of the new order
of things, or who were powerful agents in bringing it about, were
all born during the fifteenth century, four of them at least, at
so nearly the same time as to be contemporaries.

Leonardo da Vinci, whose artistic genius has charmed succeeding
generations, was also the first practical engineer of his time,
and the first man after Archimedes to make a substantial advance
in developing the laws of motion. That the world was not prepared
to make use of his scientific discoveries does not detract from
the significance which must attach to the period of his birth.

Shortly after him was born the great navigator whose bold spirit
was to make known a new world, thus giving to commercial
enterprise that impetus which was so powerful an agent in bringing
about a revolution in the thoughts of men.

The birth of Columbus was soon followed by that of Copernicus, the
first after Aristarchus to demonstrate the true system of the
world. In him more than in any of his contemporaries do we see the
struggle between the old forms of thought and the new. It seems
almost pathetic and is certainly most suggestive of the general
view of knowledge taken at that time that, instead of claiming
credit for bringing to light great truths before unknown, he made
a labored attempt to show that, after all, there was nothing
really new in his system, which he claimed to date from Pythagoras
and Philolaus. In this connection it is curious that he makes no