d values of many other
astronomical constants, but singularly enough made no determination of
the distance of the sun, adopting instead the ancient and erroneous
value given by Hipparchus.

His magnificent Observatory of Uraniborg, the finest building for
astronomical purposes that the world had hitherto seen, was allowed to
fall into decay, and scarcely more than mere indications of the site may
now be seen.

CHAPTER IV.

KEPLER JOINS TYCHO.

The association of Kepler with Tycho was one of the most important
landmarks in the history of astronomy. The younger man hoped, by the aid
of Tycho's planetary observations, to obtain better support for some of
his fanciful speculative theories, while the latter, who had certainly
not gained in prestige by leaving Denmark, was in great need of a
competent staff of assistants. Of the two it would almost seem that
Tycho thought himself the greater gainer, for in spite of his reputation
for brusqueness and want of consideration, he not only made light of
Kepler's apology in the matter of Reymers, but treated him with uniform
kindness in the face of great rudeness and ingratitude. He begged him to
come "as a welcome friend," though Kepler, very touchy on the subject of
his own astronomical powers, was afraid he might be regarded as simply a
subordinate assistant. An arrangement had been suggested by which Kepler
should obtain two years' leave of absence from Gratz on full pay, which,
because of the higher cost of living in Prague, should be supplemented
by the Emperor; but before this could be concluded, Kepler threw up his
professorship, and thinking he had thereby also lost the chance of going
to Prague, applied to Maestlin and others of his Tuebingen friends to
make interest for him with the Duke of Wurtemberg and secure the
professorship of medicine. Tycho, however, still urged him to come to
Prague, promising to do his utmost to secure for him a permanent
appointment, or in any event to see that he was not the loser by coming.
Kepler was delayed by illness on the way, but ultimately reached Prague,
accompanied by his wife, and for some time lived entirely at Tycho's
expense, writing by way of return essays against Reymers and another
man, who had claimed the credit of the Tychonic system. This Kepler
could do with a clear conscience, as it was only a question of priority
and did not involve any support of the system, which he deemed far
inferior to that of Coper