Dutchman, had invented a glass by means of which distant objects appeared as if they were near, he turned his attention to this subject, and from the imperfect accounts which he had received, and his own reflections on the nature of refraction, discovered the construction of that instrument. The next day, after he had solved the problem of its construction, he made such an instrument, and by the attention which he paid to its perfection and improvement, may justly be considered as the second inventor of the telescope. He now turned his instrument towards the heavens, and discovered unheard-of wonders. He perceived the surface of the moon not to be smooth, but rough, and full of prominences and cavities. The milky-way he found to be an assemblage of fixed stars, invisible to the naked eye. Venus he found to vary in its phases like the moon. The figure of Saturn he observed to be oblong, and imagined that it consisted of three distinct parts, one spherical in the midst, and two lesser ones on the sides, which afterwards appeared to be only the ansa, or extreme parts of Saturn's ring. Jupiter he saw surrounded with four moons, which in honour of the duke de Medici he called Medicean stars, and soon perceived that by means of their frequent eclipses geographical longitudes might be found. On the sun's disk he perceived spots, from the motion of which he inferred that the sun revolved on its axis. It was while he was pursuing these discoveries, 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 necessary for him, in the year 1615, to appear in that city to justify himself. According to letters written from Rome by the learned Anthony Querenghi, Galileo did not lose his courage on this occasion, but in numerous companies of men of letters and others, defended the Copernican doctrine with a force of argument which persuaded many of its truth and reasonableness, and silenced the objections of others who would not be convinced. When he attended the Inquisition, however, he was not suffered to enter into any

explanations, but was directly accused of heresy for maintaining 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 immoveable, but moves with a diurnal motion. These propositions he was by a decree of the Inquisitors ordered to renounce, and not to defend them either in conversation or writing, or even to insinuate them into the minds of any persons whomsoever. Most accounts concur 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 accounts he was treated with greater mildness, and only threatened with imprisonment if he should prove 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 himself on his behalf, as well as some persons of high rank and influence at the papal court. Galileo now returned to his studies, in which his astronomical observations and other happy discoveries served to establish 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 remarks 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 favour of the Copernican as sufficiently indicated 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 appearance, before the cry of heresy was raised more loudly than ever against Galileo, and he was again cited to appear before the tribunal of the Inquisition, 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 at first committed prisoner to the apartments of the fiscal 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 process

was carrying on against him. After his trial had lasted about two months. he 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-weck the seven penitential psalms, the court reserving to themselves the power of moderating, changing, and taking away, altogether, or in part, the abovementioned 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 rigour 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 Sienna, 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 Arcetri, 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 celestial 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 philosophical resignation, employing himself in constant meditation and enquiry, the result of which he intended to communicate to the world. He had digested much matter, and had begun to dictate his conceptions, when he was attacked by a distemper 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 constitution. His learning was very extensive; and he possessed in a high degree, a clearness and acuteness of wit. In company he was free and affable, and full of pleasantry. He took great delight in architecture and painting, and designed extremely well; and he also played on the lute with great skill and taste. Whenever he spent any part of his time in the country, he took great pleasure in husbandry. From the time of Archimedes, as M. Leibnitz

observes, there had been nothing done in mechanical geometry, till Galileo, who possessed an excellent judgment, and great skill in the most abstruse points of geometry, first extended 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 summary sketch of his discoveries and improvements, chiefly in the language of the judicious Colin Maclaurin. "He made the evidence of the Copernican system more sensible, when he shewed 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 diurnal rotation of the earth became more credible. The four satellites that attended 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 revolution. By discovering hills and cavities in the moon, and spots in the sun constantly varying, he shewed that there was not so great a difference between celestial and sublunary bodies as the philosophers had vainly imagined. He rendered no less service to science by treating, in a clear and geometrical manner, the doctrine of motion, which has been justly called the Key of Nature. The rational part of mechanics had been so much neglected, that scarcely any improvement was made in it for almost two thousand years; but Galileo has given us fully the theory of equable motions, and of such as are uniformly accelerated or retarded, and of these two compounded together. He, first, demonstrated, that the spaces described by heavy bodies from the beginning of their descent are as the squares of the times; and that a body, projected in any direction that is not perpendicular to the hori zon, describes a parabola. These were the beginnings of the doctrine of the motion of heavy bodies, which has been since carried to so great a

height by sir Isaac Newton. In geometry, he invented the Cycloid, or Trochoid; though the properties of it were afterwards chiefly demonstrated by his pupil Torricelli. He invented the simple pendulum, and made use of it in his astronomical experiments: he had also thoughts of applying it to clocks; but did not execute that design. The glory of that invention was reserved for his son Vincenzo, who made the experiment at Venice in 1649; and Huygens afterwards carried the invention to perfection. Of Galileo's invention also was the machine

with which the Venetians render their Laguna fluid and navigable. He also discovered the gravity of the air, and endeavoured to compare it with that of water; and opened up several other enquiries in natural philosophy. He was not esteemed and followed by philosophers only, but was honoured by persons of the greatest dis tinction of all nations. Galileo had scholars worthy of so great a master, by whom the gravitation of the atmosphere was established fully, and its varying pressure accurately and conveniently measured, by the column of quicksilver of equal weight sustained by it in the barometrical tube. The elasticity of the air, by which it perpetually endeavours to expand itself, and, while it admits of condensation, resists in proportion to its density, was a phenomenon of a new kind (the common fluids having no such property), and of the utmost importance to philosophy. These principles opened a vast field of new and useful knowledge, and explained a great variety of phenomena, which had been accounted for in an absurd manner before that time. It seemed as if the air, the fluid in which men lived from the beginning, had been then first discovered. Philosophers were everywhere busy enquiring into the various properties and their effects; and valuable discoveries rewarded their industry. Of the great number who distinguished themselves on this occasion, we cannot but mention Torricelli and Viviani in Italy, Pascal in France, Otto Guerick in Germany, and Boyle in England." Galileo wrote a number of treatises, of which the principal, published during his life-time, besides his "Mechanics," "Balance," and "Dialogues," already mentioned, were, "The Operations of the Compass, geometrical and military," 1606; " A Discourse addressed to the most serene, Cosmo II., Grand-duke of Tuscany, concerning the Swimming of Bodies upon, and their Submersion in, Water," 1612; "Nuncius Sidereus," 1610, of which "A Continuation," or "An Essay on the History of Galileo's last Observations on Saturn, Mars, Venus, and the Sun, &c." was afterwards collected from letters between Galileo and his correspondents; "A Letter concerning the Trepidation of the Moon, lately discovered, inscribed to Alphonso Antonini, with Antonini's Answer," 1638; "A Discourse of the solar Spots, &c. with Predictions and Ephemerides of the Medicean Planets," 1613; the famous Italian piece entitled "Il Saggiatore," written in de fence of Guiducci's Discourse on Comets," and containing a complete account of the physiology and astronomy of our author, printed in

1623; "A Letter to Prince Leopold of Tuscany, examining the fiftieth Chapter of Licetus's Letheosphoros;" "A Letter to Christopher Greinbergerus, concerning the Montuosity of the Moon," 1611;"Mathematical Discourses and Demonstrations concerning two new Sciences, relating to Mechanics and local Motions, together with an Appendix concerning the Centre of Gravity in some Solids," 1638, &c. The preceding articles, together with some other treatises written either by Galileo, or by some of his disciples in defence of his doctrines and observations, were collected and published by Menolessi, in 1656, under the title of "L'Opere de Galileo Galilei Lynceo, nobile Fiorentino, &c." in two volumes quarto. Several of these pieces were translated into English, and published by Thomas Salisbury, in his "Mathematical Collections," in two volumes folio. A volume also of his "Letters" to several learned men, and solutions of a variety of problems, was published at Bologna, in quarto. His last disciple, Vincenzo Viviani, who proved a very eminent mathematician, methodised a piece of his master's, and published it under the title of "Quinto Libro de gli Elementi d'Euclide, &c." 1674, quarto; and he also published some other pieces of Galileo, including extracts from his Letters to a learned Frenchman, in which the author gives an account of the works which he intended to have published, and an extract of a Letter to John Camillo, a mathematician of Naples, concerning the angle of contact. Many other of Galileo's writings were unfortunately lost to the world, owing to the superstition of one of his ignorant nephews; who, considering that his uncle died a prisoner of the holy office, though permitted to reside in his own house, suspected that his papers might contain dangerous heresies, and therefore committed them to the flames. Sir John Finch, in a Letter to Thomas Salisbury, attributes the destruction of Galileo's MSS. to his widow's devotion, and the fanaticism of her confessor; but the best authorities maintain that our philosopher was never married. His son VINCENZO GALILEI, who, as we have already seen, honourably supported his father's repu tation, by first applying his invention of the pendulum to clock-work, was of illegitimate birth.

VINCENZO GALILEI, the father of Galileo, was a man of letters, not unskilled in the mathematics, and particularly conversant in the science of music. He wrote some elaborate works, of which the most esteemed consist of five dialogues concerning harmony, and its.

was carrying on against him. After his trial had lasted about two months. he 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-weck the seven penitential psalms, the court reserving to themselves the power of moderating, changing, and taking away, altogether, or in part, the abovementioned 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 rigour 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 Sienna, 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 Arcetri, 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 celestial 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 philosophical resignation, employing himself in constant meditation and enquiry, the result of which he intended to communicate to the world. He had digested much matter, and had begun to dictate his conceptions, when he was attacked by a distemper 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 constitution. His learning was very extensive; and he possessed in a high degree, a clearness and acuteness of wit. In company he was free and affable, and full of pleasantry. He took great delight in architecture and painting, and designed extremely well; and he also played on the lute with great skill and taste. Whenever he spent any part of his time in the country, he took great pleasure in husbandry. From the time of Archimedes, as M. Leibnitz

observes, there had been nothing done in mechanical geometry, till Galileo, who possessed an excellent judgment, and great skill in the most abstruse points of geometry, first extended 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 summary sketch of his discoveries and improvements, chiefly in the language of the judicious Colin Maclaurin. "He made the evidence of the Copernican system more sensible, when he shewed 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 diurnal rotation of the earth became more credible. The four satellites that attended 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 revolution. By discovering hills and cavities in the moon, and spots in the sun constantly varying, he shewed that there was not so great a difference between celestial and sublunary bodies as the philosophers had vainly imagined. He rendered no less service to science by treating, in a clear and geometrical manner, the doctrine of motion, which has been justly called the Key of Nature. The rational part of mechanics had been so much neglected, that scarcely any improvement was made in it for almost two thousand years; but Galileo has given us fully the theory of equable motions, and of such as are uniformly accelerated or retarded, and of these two compounded together. He, first, demonstrated, that the spaces described by heavy bodies from the beginning of their descent are as the squares of the times; and that a body, projected in any direction that is not perpendicular to the horizon, describes a parabola. These were the beginnings of the doctrine of the motion of heavy bodies, which has been since carried to so great a

height by sir Isaac Newton. In geometry, he invented the Cycloid, or Trochoid; though the properties of it were afterwards chiefly demonstrated by his pupil Torricelli. He invented the simple pendulum, and made use of it in his astronomical experiments: he had also thoughts of applying it to clocks; but did not execute that design. The glory of that invention was reserved for his son Vincenzo, who made the experiment at Venice in 1649; and Huygens afterwards carried the invention to perfection. Of Galileo's invention also was the machine