al skill, always at the service of the
poor, was frequently in demand by the rich; and he laid a scheme for the
reform of the currency before the Diet of Graudenz in 1522. Yet he found
time, amid these multifarious occupations, to elaborate an entirely new
system of astronomy, by the adoption of which man's outlook on the
universe was fundamentally changed.

The main lines of his great work were laid down at Heilsberg; at
Frauenburg, from 1513, he sought, with scanty instrumental means, to
test by observation the truth of the views it embodied (see ASTRONOMY:
HISTORY). His dissatisfaction with Ptolemaic doctrines was of early
date; and he returned from Italy, where so-called Pythagorean opinions
were then freely discussed, in strong and irrevocable possession of the
heliocentric theory. The epoch-making treatise in which it was set
forth, virtually finished in 1530, began to be known through the
circulation in manuscript of a _Commentariolus_, or brief popular
account of its purport written by Copernicus in that year. Johann
Albrecht Widmanstadt lectured upon it in Rome; Clement VII. approved,
and Cardinal Schonberg transmitted to the author a formal demand for
full publication. But his assent to this was only extracted from him in
1540 by the importunities of his friends, especially of his enthusiastic
disciple George Joachim Rheticus (1514-1576), who printed, in the
_Narratio prima_ (Danzig, 1540), a preliminary account of the Copernican
theory, and simultaneously sent to the press at Nuremberg his master's
complete exposition of it in the treatise entitled _De revolutionibus
orbium coelestium_ (1543). But the first printed copy reached Frauenburg
barely in time to be laid on the writer's death-bed. Copernicus was
seized with apoplexy and paralysis towards the close of 1542, and died
on the 24th of May 1543, happily unconscious that the fine Epistle, in
which he had dedicated his life's work to Paul III., was marred of its
effect by an anonymous preface, slipt in by Andreas Osiander
(1498-1552), with a view to disarming prejudice by insisting upon the
purely hypothetical character of the reasonings it introduced. The
trigonometrical section of the book had been issued as a separate
treatise (Wittenberg, 1542) under the care of Rheticus. The only work
published by Copernicus on his own initiative was a Latin version of the
Greek Epistles of Theophylact (Cracow, 1509). His treatise _De monetae
cudendae ratione_, 1526 (f