of the name is a modern
science: it dates from the sixteenth century only. Three great, three
brilliant phases have marked its progress. In 1543 the bold and firm
hand of Copernicus overthrew the greater part of the venerable
scaffolding which had propped the illusions and the pride of many
generations. The earth ceased to be the centre, the pivot, of celestial
movements. Henceforward it ranged itself modestly among the other
planets, its relative importance as one member of the solar system
reduced almost to that of a grain of sand.

Twenty-eight years had elapsed from the day when the Canon of Thorn
expired while holding in his trembling hands the first copy of the work
which was to glorify the name of Poland, when Wuertemberg witnessed the
birth of a man who was destined to achieve a revolution in science not
less fertile in consequences, and still more difficult to accomplish.
This man was Kepler. Endowed with two qualities which seem
incompatible,--a volcanic imagination, and a dogged pertinacity which
the most tedious calculations could not tire,--Kepler conjectured that
celestial movements must be connected with each other by simple laws;
or, to use his own expression, by harmonic laws. These laws he undertook
to discover. A thousand fruitless attempts--the errors of calculation
inseparable from a colossal undertaking--did not hinder his resolute
advance toward the goal his imagination descried. Twenty-two years he
devoted to it, and still he was not weary. What are twenty-two years of
labor to him who is about to become the lawgiver of worlds; whose name
is to be ineffaceably inscribed on the frontispiece of an immortal code;
who can exclaim in dithyrambic language, "The die is cast: I have
written my book; it will be read either in the present age or by
posterity, it matters not which; it may well await a reader since God
has waited six thousand years for an interpreter of his works"?

These celebrated laws, known in astronomy as Kepler's laws, are three in
number. The first law is, that the planets describe ellipses around the
sun, which is placed in their common focus; the second, that a line
joining a planet and the sun sweeps over equal areas in equal times; the
third, that the squares of the times of revolution of the planets about
the sun are proportional to the cubes of their mean distances from that
body. The first two laws were discovered by Kepler in the course of a
laborious examination of the theo