LESIEUR-DESAULNIERS, Isaac (les-yurr), Canadian educator, born in Ste. Anne d'Yaamchiche, Lower Canada, 28 November, 1811; died in the College of St. Hyacinthe, Canada. 5 April, 1868. He was graduated at the College of Nicolet in 1828, and, notwithstanding his youth, was appointed professor of philosophy in the College of St. Hyacinthe. He was ordained priest in 1838, and in 1847 travelled through every part of Canada, collecting funds for a new college at St. Hyacinthe, which was built almost entirely by his energy and devotion. After travelling in Europe, Asia, and Africa, in 1852-'4 he was appointed superior of the college, and remodelled the entire system of teaching, doing away almost wholly with punishments, and appealing successfully to the honor of his students. He wrote an unpublished translation of part of the "Summa" of St. Thomas Aquinas, and a "Traite des obligations" for the benefit of his pupils. In 1867 he published a remarkable series of articles on "Le progres" in the "Courrier de St. Hyacinthe." On questions of ecclesiastical law he was the authority of the priests of his own and neighboring dioceses. In 1849-'50 he delivered a course of lectures before the Canadian institute of Montreal on "Being," and one on the "Physical and Intellectual Organization of Man" before the School of medicine, which attracted wide attention. About this time he engaged in an interesting public discussion on the subject of electricity with Dr. Meilleur and the Abbe Duchaine.