is and a gradual decay of
his mental and vital powers. His book was printed at Nuremberg, and the
first copy arrived at Frauenburg on May 24, 1543, in time to be touched
by the hands of the dying man, who in a few hours after expired. The
house in which Copernicus lived at Allenstein is still in existence, and
in the walls of his chamber are visible the perforations which he made
for the purpose of observing the stars cross the meridian.

Copernicus was the means of creating an entire revolution in the science
of astronomy, by transferring the centre of our system from the Earth to
the Sun. He accounted for the alternation of day and night by the
rotation of the Earth on her axis, and for the vicissitudes of the
seasons by her revolution round the Sun. He devoted the greater part of
his life to meditating on this theory, and adduced several weighty
reasons in its support. Copernicus could not help perceiving the
complications and entanglements by which the Ptolemaic system of the
universe was surrounded, and which compared unfavourably with the simple
and orderly manner in which other natural phenomena presented themselves
to his observation. By perceiving that Mars when in opposition was not
much inferior in lustre to Jupiter, and when in conjunction resembled a
star of the second magnitude, he arrived at the conclusion that the
Earth could not be the centre of the planet's motion. Having discovered
in some ancient manuscripts a theory, ascribed to the Egyptians, that
Mercury and Venus revolved round the Sun, whilst they accompanied the
orb in his revolution round the Earth, Copernicus was able to perceive
that this afforded him a means of explaining the alternate appearance of
those planets on each side of the Sun. The varied aspects of the
superior planets, when observed in different parts of their orbits, also
led him to conclude that the Earth was not the central body round which
they accomplished their revolutions. As a combined result of his
observation and reasoning Copernicus propounded the theory that the Sun
is the centre of our system, and that all the planets, including the
Earth, revolve in orbits around him. This, which is called the
Copernican system, is now regarded as, and has been proved to be, the
true theory of the solar system.

TYCHO BRAHE was a celebrated Danish astronomer, who earned a deservedly
high reputation on account of the number and accuracy of his
astronomical observations and calculat