the later decades of his life. He himself tells us that he had
even questioned whether it were not better for him to confine
himself to such verbal teaching, following thus the example of
Pythagoras. Just as his life was drawing to a close, he decided
to pursue the opposite course, and the first copy of his work is
said to have been placed in his hands as he lay on his deathbed.

The violent opposition which the new system met from
ecclesiastical sources led subsequent commentators to suppose
that Copernicus had delayed publication of his work through fear
of the church authorities. There seems, however, to be no direct
evidence for this opinion. It has been thought significant that
Copernicus addressed his work to the pope. It is, of course,
quite conceivable that the aged astronomer might wish by this
means to demonstrate that he wrote in no spirit of hostility to
the church. His address to the pope might have been considered as
a desirable shield precisely because the author recognized that
his work must needs meet with ecclesiastical criticism. Be that
as it may, Copernicus was removed by death from the danger of
attack, and it remained for his disciples of a later generation
to run the gauntlet of criticism and suffer the charges of
heresy.

The work of Copernicus, published thus in the year 1543 at
Nuremberg, bears the title De Orbium Coelestium Revolutionibus.

It is not necessary to go into details as to the cosmological
system which Copernicus advocated, since it is familiar to every
one. In a word, he supposed the sun to be the centre of all the
planetary motions, the earth taking its place among the other