em applies, if at all, rather to an
earlier--its nebulous--stage, when the whole thing was one great whirl,
ready to split or shrink off planetary rings at their appropriate
distances.

Soon after he had written his great work, the _Principia Mathematica_,
and before he printed it, news reached him of the persecution and
recantation of Galileo. "He seems to have been quite thunderstruck at
the tidings," says Mr. Mahaffy, in his _Life of Descartes_.[15] "He had
started on his scientific journeys with the firm determination to enter
into no conflict with the Church, and to carry out his system of pure
mathematics and physics without ever meddling with matters of faith. He
was rudely disillusioned as to the possibility of this severance. He
wrote at once--apparently, November 20th, 1633--to Mersenne to say he
would on no account publish his work--nay, that he had at first resolved
to burn all his papers, for that he would never prosecute philosophy at
the risk of being censured by his Church. 'I could hardly have
believed,' he says, 'that an Italian, and in favour with the Pope as I
hear, could be considered criminal for nothing else than for seeking to
establish the earth's motion; though I know it has formerly been
censured by some Cardinals. But I thought I had heard that since then it
was constantly being taught, even at Rome; and I confess that if the
opinion of the earth's movement is false, all the foundations of my
philosophy are so also, because it is demonstrated clearly by them. It
is so bound up with every part of my treatise that I could not sever it
without making the remainder faulty; and although I consider all my
conclusions based on very certain and clear demonstrations, I would not
for all the world sustain them against the authority of the Church.'"

Ten years later, however, he did publish the book, for he had by this
time hit on an ingenious compromise. He formally denied that the earth
moved, and only asserted that it was carried along with its water and
air in one of those larger motions of the celestial ether which produce
the diurnal and annual revolutions of the solar system. So, just as a
passenger on the deck of a ship might be called stationary, so was the
earth. He gives himself out therefore as a follower of Tycho rather than
of Copernicus, and says if the Church won't accept this compromise he
must return to the Ptolemaic system; but he hopes they won't compel him
to do that, seeing that i