astronomy. Recognising the inevitable errors of workmanship in his
little instrument, he ascertained their amount and allowed for their
influence on the results which he deduced. This principle, employed
by the boy with his cross-staff in 1564, is employed at the present
day by the Astronomer Royal at Greenwich with the most superb
instruments that the skill of modern opticians has been able to
construct.

[PLATE: TYCHO'S TRIGONIC SEXTANT.
(The arms, AB and AC, are about 5 1/2 ft. long.)]

After the death of his uncle, when Tycho was nineteen years of age,
it appears that the young philosopher was no longer interfered with
in so far as the line which his studies were to take was concerned.
Always of a somewhat restless temperament, we now find that he
shifted his abode to the University of Rostock, where he speedily
made himself notable in connection with an eclipse of the moon on
28th October, 1566. Like every other astronomer of those days, Tycho
had always associated astronomy with astrology. He considered that
the phenomena of the heavenly bodies always had some significance in
connection with human affairs. Tycho was also a poet, and in the
united capacity of poet, astrologer, and astronomer, he posted up
some verses in the college at Rostock announcing that the lunar
eclipse was a prognostication of the death of the great Turkish
Sultan, whose mighty deeds at that time filled men's minds. Presently
news did arrive of the death of the Sultan, and Tycho was accordingly
triumphant; but a little later it appeared that the decease had taken
place BEFORE the eclipse, a circumstance which caused many a laugh at
Tycho's expense.