e announces his intention to defend the Copernican system,
as a pure mathematical hypothesis, and not as an opinion having an
advantage over that of the stability of the earth absolutely. The
dialogue is conducted by three persons, Salviati, Sagredo, and
Simplicio. Salviati, who is the true philosopher in the dialogue, was
the real name of a nobleman whom we have already had occasion to
mention. Sagredo, the name of another noble friend of Galileo's,
performs a secondary part under Salviati. He proposes doubts, suggests
difficulties, and enlivens the gravity of the dialogue with his wit and
pleasantry. Simplicio is a resolute follower of Ptolemy and Aristotle,
and, with a proper degree of candour and modesty, he brings forward all
the common arguments in favour of the Ptolemaic system. Between the wit
of Sagredo, and the powerful philosophy of Salviati, the peripatetic
sage is baffled in every discussion; and there can be no doubt that
Galileo aimed a more fatal blow at the Ptolemaic system by this mode of
discussing it, than if he had endeavoured to overturn it by direct
arguments.

The influence of this work on the public mind was such as might have
been anticipated. The obnoxious doctrines which it upheld were eagerly
received, and widely disseminated; and the church of Rome became
sensible of the shock which was thus given to its intellectual
supremacy. Pope Urban VIII., attached though he had been to Galileo,
never once hesitated respecting the line of conduct which he felt
himself bound to pursue. His mind was, nevertheless, agitated with
conflicting sentiments. He entertained a sincere affection for science
and literature, and yet he was placed in the position of their enemy. He
had been the personal friend of Galileo, and yet his duty compelled him
to become his accuser. Embarrassing as these feelings were, other
considerations contributed to soothe him. He had, in his capacity of a
Cardinal, opposed the first persecution of Galileo. He had, since his
elevation to the pontificate, traced an open path for the march of
Galileo's discoveries; and he had finally endeavoured to bind the
recusant philosopher by the chains of kindness and gratitude. All these
means, however, had proved abortive, and he was now called upon to
support the doctrine which he had subscribed, and administer the law of
which he was the guardian.

It has been supposed, without any satisfactory evidence, that Urban may
have been influenced by