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 246 GREGORY soon after published a treatise on the quadra- ture of the circle and hyperbola by means of a converging series, which involved him in a controversy with Huygens. About 1668 he was chosen professor of mathematics at St. Andrews. In 1674 he accepted the same chair in Edinburgh, and a year later was struck with sudden blindness, and died a few days afterward. He was the inventor of the concave burning mirror, of methods for squar- ing curves and making logarithms by an in- finitely converging series, and of a variety of other ingenious mathematical and geometrical processes. II. David, nephew of the preceding, born in Aberdeen, June 24, 1661, died about 1710. He was educated at the university of Edinburgh, where he was appointed professor of mathematics in 1684, and was instrumental in introducing the Newtonian philosophy. In the same year he published a Latin treatise on the dimensions of figures, Exercitatio Geo- metrica, which is esteemed his best work. In 1692, chiefly through the influence of Flam- steed and Sir Isaac Newton, he was appointed Savilian professor of astronomy at Oxford, the celebrated Dr. Halley being his competi- tor. In 1702 appeared his Astronomice Physica et Geometric^ Elementa, a sort of digest of Newton's Principia, which Newton himself highly commended ; and in 1703 he published an edition of Euclid in Greek and Latin. He was engaged at the time of his death upon an edition of Apollonius, which was completed by Halley. Newton intrusted Gregory with a manuscript copy of his Principia, and in a second edition availed himself of his friend's marginal comments. III. John, grandson of James Gregory, born in Aberdeen, June 3, 1724, died in Edinburgh, Feb. 10, 1773. He graduated in medicine at the university of Aberdeen, where he filled the chair of medi- cine from 1756 to 1764, when he removed to Edinburgh. From 1766 till his death he was professor of the practice of physic in the uni- versity of Edinburgh. His principal works are "Elements of the Practice of Physic" (Edinburgh, 1772), left unfinished, and "A Father's Legacy to his Daughters " (1774). GREGORY, Ollnthns Gilbert, an English mathe- matician, born in Yaxley, Huntingdonshire, Jan. 29, 1774, died in Woolwich, Feb. 2, 1841. He wrote a treatise on the "Use of the Sliding Rule," a "Treatise on Astronomy," and in 1802, in connection with Dr. John Mason Good, undertook to edit the " Pantalogia," a cyclo- paedia of the arts and sciences. He was ap- pointed a mathematical master at the royal military academy at Woolwich, and in 1806 was raised to the professor's chair, which he held till June, 1838. Ills principal works are a "Treatise on Astronomy," a "Treatise on Mechanics," the " Evidences of Christianity," and " Memoirs " of the Rev. Robert Hall and Dr. John Mason Good. GRKGORY THE ILLUMINATOR, a saint of the church, the apostle and first patriarch of Ar- GREGORY NAZIANZEN menia, born in 257, died about 332. He was the son of Anag, a prince of the royal family of the Arsacidse, who having assassinated Chosroes, king of Armenia, was put to death with all his family except Gregory, then two years old. Gregory was taken to Ca3sarea in Cappadocia by a Christian nurse, and on becoming of age was there married, but sep- arated from his wife three years later by mu- tual consent. He went to Rome, attached him- self to the suite of Tiridates III., king of Ar- menia, and accompanied him to that country, where, having refused to sacrifice to idols, he was subjected to various tortures, and finally cast into a dungeon near Artaxata. A benev- olent widow supported him here for 14 years. At the end of that time the king, who is said to have been cured by his prayers of a despe- rate malady, embraced the faith (302). The saint afterward went to Caesarea, and was consecrated metropolitan of Armenia. Return- ing to that country, he preached the gospel both E. and W. of the Euphrates, baptized many, destroyed pagan temples, built churches, ordained priests, and, having converted most of the nation, consecrated his son Arisdages as his successor in 318. In 325 he and the king were invited by Constantine to the council at Nice. In 331 he withdrew into a cavern, where he died. GREGORY NAZIANZEN, a saint and doctor of the church, born about 328, died about 389. His father Gregory, a convert from heathen- ism, was on account of his holy life and great zeal made bishop of Nazianzus in Cappadocia, which see he governed 45 years, and died when about 90 years old. He and Nonna, the moth- er of the saint, are recognized as saints in the calendars of the church. The son was care- fully educated in the schools of Csesarea, Al- exandria, and Athens, and had for fellow stu- dents Basil the Great, Gregory of Nyssa, and Julian the Apostate. At his return to Nazi- anzus he was baptized, and lived austerely as a hermit in company with St. Basil. After some time thus spent in study and religious ex- ercises, he was recalled to Nazianzus, was or- dained priest, and assisted his father in the government of his diocese. He fled again for a time to the desert, but fearing to incur the displeasure of heaven by shrinking from his work, he returned to Nazianzus, and on Easter Sunday preached his first sermon. He is con- sidered by many as the most eloquent of all the fathers of the church. His addresses are fervid, florid, and fanciful, for Gregory was a poet, and wrote much in verse as well as in prose. Among his early discourses were two of great severity against the emperor Julian. In 372 he was consecrated by St. Basil bishop of Sasima ; but being prevented from occupying that see, he remained to help his father at Nazianzus. In 378 the death of the emperor ' Valens restored peace to the church, and the pastors everywhere sought to revive in their churches their pristine glory, obscured by 40