h of those psychic
agencies which started men on new lines of thought, then surely was the
fifteenth the wonderful century.

Let us not forget that, in assigning the actors then born to their
places, we are not narrating history, but studying a special phase of
evolution. It matters not for us that no university invited Leonardo to
its halls, and that his science was valued by his contemporaries only
as an adjunct to the art of engineering. The great fact still is that
he was the first of mankind to propound laws of motion. It is not for
anything in Luther's doctrines that he finds a place in our scheme. No
matter for us whether they were sound or not. What he did towards the
evolution of the scientific investigator was to show by his example
that a man might question the best-established and most venerable
authority and still live--still preserve his intellectual
integrity--still command a hearing from nations and their rulers. It
matters not for us whether Columbus ever knew that he had discovered a
new continent. His work was to teach that neither hydra, chimera nor
abyss--neither divine injunction nor infernal machination--was in the
way of men visiting every part of the globe, and that the problem of
conquering the world reduced itself to one of sails and rigging, hull
and compass. The better part of Copernicus was to direct man to a
view-point whence he should see that the heavens were of like matter
with the earth. All this done, the acorn was planted from which the oak
of our civilization should spring. The mad quest for gold which
followed the discovery of Columbus, the questionings which absorbed the
attention of the learned, the indignation excited by the seeming
vagaries of a Paracelsus, the fear and trembling lest the strange
doctrine of Copernicus should undermine the faith of centuries, were
all helps to the germination of the seed--stimuli to thought which
urged it on to explore the new fields opened up to its occupation. This
given, all that has since followed came out in regular order of
development, and need be here considered only in those phases having a
special relation to the purpose of our present meeting.

So slow was the growth at first that the sixteenth century may scarcely
have recognized the inauguration of a new era. Torricelli and Benedetti
were of the third generation after Leonardo, and Galileo, the first to
make a substantial advance upon his theory, was born more than a
century afte