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, a learned Italian mathe. matician, was born at Milan, Nov. 17, 1702. He was educated among the Jesuits, and entered into their order in 1718. He afterwards taught the belles-lettres at Vercelli and Pavia, and was appointed rhetoric- professor in the university of Brera, in Milan. In 1733 the senate of Milan appointed him professor of mathematics at Pavia, and afterwards removed him to the same office at Milan, the duties of which he executed with reputation for twenty years. In F75J) his fame procured him an invitation to Vienna from the empress Maria Teresa, who honoured him with her esteem, and appointed him mathematician to the court, with a pension of 500 florins. What rendered him most celebrated, was the skill he displayed as superintendant and chief director of the processes for measuring the bed of the Reno and other less considerable rivers belonging to Bologna, Ferrara, and Ravenna. On this he was employed for six years, under Clement XIII.; and Clement XIV. ordered that these experiments should be continued upon Leccln’s plans. He died August 24, 1776, aged seventy-three years. Fabroni, who has given an excellent personal character of Lecchi, and celebrates his skill in hydraulics, has, contrary to his usual practice, mentioned his works only in a general way; and for the following list we have therefore been obliged to have recourse to a less accurate authority: 1. “Theoria lucis,” Milan, 1739. 2. “Arithmetica universalis Jsaaci Newton, sive de compositione, et resolutione arithmetica perpetuis commentariis illustrata et aucta,” Milan, 1752, 3 vols. 8vo. 3. “Elementa geometrise theoricx et practices,” ibid. 1753, 2 vols. 8vo. 4. “Elementa Trigonometric,” &c. ibid. 1756. 5. “De sectionibus conicis,” ibid. 1758. 6. “Idrostatica csaaiinata,” &c. ibid. 1765, 4 to. 7. “Relazione della visita alle terre dannegiate dalle acque di Bologna, Ferrara, e Ravenna,” &c. Rome, 17G7, 4to. 8. “Memorie idrostatico-storiche delle operazioni esequite nella inalveazione del Reno di Bologna, e degli altri minori torrenti per la linea di primaro al mare dalP anno 1765 al 1772,” Modena, 1775, 2 vols. 4to. 9. “Trattato de' canali navigabili,” Milan, 1776, 4to.