It was while he was pursuing these dis coveries, that he was invited to Florence, where, as we have seen, he had leisure afforded him to devote himself to his mathematical and philosophical studies, without being obliged to attend to the duties of his professorship. In a very few years, however, his tranquillity was disturbed by the ignorant and bigotted clergy, on account of the zeal which he discovered for illustrating and confirming the truth of the Copernican system. That system they maintained to be false and heretical, as being contrary to the plain and express language of the scriptures ; and by their complaints against him to the Inquisition at Rome, rendered it ne cessary for him, in the year 1615, to ap pear in that city to justify himself. Ac cording to letters written from Rome, by the learned Anthony Quezenghi, Ga lileo did not lose his courage on this oc casion, but, in numerous companies of men of letters and others, defended the Copernican doctrine with a force of argu ment, which persuaded many of its truth and reasonableness, and silenced the ob jections of others, who would not be con vinced. When he attended the Inquisi tion, however, he was not suffered to enter into any explanations, but was directly accused of heresy for maintain ing the two propositions, that the sun is the centre of the world, and immoveable by a local motion, and that the earth is not the centre of the world, nor im moveable, but moves with a diurnal mo tion. These propositions he was order ed.by a decree of the Inquisitors to re. nounce, and not, to defend them either in conversation or writing, or even to in sinuate them into the minds of any per sons whomsoever. Most accounts con. cur in stating, that, on this occasion, he was committed to the prison of the Holy Office, where he was confined for about five months; but, according to other ac counts, he was treated with greater mild. ness, and only threatened with imprison.. ment if he proved refractory. Be that as it may, he was not permitted to quit Rome until he had promised to conform himself to the decree of the Inquisition ; and it is probable that his sentence would have been more severe, had not the Grand Duke of Tuscany warmly interested him self on his behalf, as well as some per sons of high rank and influence at the pa. pal court.
Galileo now returned to his studies, in which his astronomical observations, and other happy discoveries, served to.estab lish most completely and satisfactorily the truth of his obnoxious opinions. From time to time he laid before the public an account of his discoveries, with such re marks and inferences as tended to point out the natural conclusions to be drawn from them. At length, in the year 1632, he ventured to publish, at Florence, his famous " Dialogues on the two greatest systems of the World, the Ptolemaic and Copernican ;" in which he produced the strongest arguments in favour of both systems, without expressing a decided opinion which of them was the true one, but not without such insinuations in fa vour of the Copernican, as sufficiently in dicated its superior reasonableness, and his own belief in it. These dialogues, likewise, contain some keen strokes of raillery against the Aristotelians, for their bigotted and servile attachment to every hypothesis of their master.
Scarcely had this work made its ap. pearance, before the cry of heresy was raised more loudly than ever against Galileo, and he was again cited to ap. pear before the tribunal of the Inquisi. tion, in the year 1633. Though now seventy years of age, he was obliged to submit to the persecuting mandate, and on his arrival at Rome was first commit. ted prisoner to the apartments of the Fis cal of the Holy Office. Afterwards, through the intercession of the Grand Duke, he was permitted to reside in the house of his embassador, while the pro cess was carrying on against him. After
his trial lied lasted about two months, ho was brought up to receive sentence in full congregation ; when he was ordered, in the most solemn manner, to abjure and condemn the Copernican system, as contrary to the Scriptures, and to bind himself, by oath, no longer to teach or support it, either directly or indirectly. As a punishment for having disobeyed the former decree of the court, he was condemned to be detained in the prisons of the Holy office, during the pleasure of the Cardinal Inquisitors, and enjoined, as a saving penance, for three years to come, to repeat, once a week, the seven penitential psalms, the court reserving to themselves the power of moderating, changing, and taking away altogether, or in part, the above-mentioned punishment and penance His dialogues were also censured, prohibited, and ordered to be burnt at Rome.
Pope Urban VIII. who at that time sat on the Pontifical throne, lessened the ri gour of his sentence, by confining him for a time to the palace and garden de Medici at Rome ; after which he was sent to the archiepiscopal palace at Si enna, where the air was more favourable to his state of health ; and in the course of the year 1634, he was permitted to reside at his country house at Ancetri, in the vicinity of Florence.
In this place he spent the remainder of his days, visited and esteemed by the most distinguished characters in Florence, and diligently applying himself to his ce lestial -observations. By his continual use of the telescope, however, and the injuries which his eyes received from the nocturnal air, his sight was gradually impaired, till he became entirely blind about three years before his death. This calamity he bore with a truly philosophi cal resignation, employing himself in con stant meditation and enquiry, the result of which he intended to communicate to the world. He had digested much mat ter, and had begun to dictate his concep tions, when he was attacked by a distem per which terminated in his death, in 1642, when he was in the seventy-eighth year of his age.
Galileo was small in stature, but of a venerable aspect, and of a vigorous con stitution. His learning was very exten sive ; and he possessed, in a high degree, a clearness and acuteness of wit. In com pany he was free and affable, and full of pleasantry.
He took great delight in Architecture and Painting, and designed extremely well; and he also plaxed on, the lute with great skill and taste. lrhenever he spent any of his time in the country, he took great pleasure in husbandry. From the time of Archimedes,. as M. Leibnitz observes, there had been no thing done in mechanical geometry, tilt Galileo, who, possessing an excellent judgment, and great skill in the most abstruse points of geometry, first extend ed the boundaries of that science, and began to reduce the resistance of solid bodies to its laws. We shall follow the example of Dr. Hutton, in giving a sum mary sketch of his discoveries and im provements, chiefly in the language of the judicious Colin Maclaurin. " He made the evidence of the Copernican system more sensible, when he showed from the phases of Venus, like to the monthly phases of the moon, that Venus actually revolves about the sun. He proved the revolution of the sun on his axis, from his spots ; and thence the di urnal rotation of the earth became more credible, The four satellites that at tended Jupiter, in his revolution about the sun, represented, in Jupiter's lesser system, a just image of the great solar system, and rendered it more easy to conceive how the moon might attend the earth, as a satellite, in her annual revolu tion. By discovering hills and cavities in the moon, and spots in the sun con stantly varying, he showed that there was not so great a difference between celes tial and sublunary bodies as the philoso phers had vainly imagined.