all rise and flow to the moon.

7. He attributes the tides to lunar attraction. Kepler had been
appointed Imperial Astronomer with a handsome salary (on paper), a
fraction of which was doled out to him very irregularly. He was led to
miserable makeshifts to earn enough to keep his family from
starvation; and proceeded to Ratisbon in 1630 to represent his claims
to the Diet. He arrived worn out and debilitated; he failed in his
appeal, and died from fever, contracted under, and fed upon,
disappointment and exhaustion. Those were not the days when men could
adopt as a profession the "research of endowment."

Before taking leave of Kepler, who was by no means a man of one idea,
it ought to be here recorded that he was the first to suggest that a
telescope made with both lenses convex (not a Galilean telescope) can
have cross wires in the focus, for use as a pointer to fix accurately
the positions of stars. An Englishman, Gascoigne, was the first to use
this in practice.

From the all too brief epitome here given of Kepler's greatest book,
it must be obvious that he had at that time some inkling of the
meaning of his laws--universal gravitation. From that moment the idea
of universal gravitation was in the air, and hints and guesses were
thrown out by many; and in time the law of gravitation would doubtless
have been discovered, though probably not by the work of one man, even
if Newton had not lived. But, if Kepler had not lived, who else could
have discovered his laws?


FOOTNOTES: