Guillon, Marie Nicholas Silvestre a French priest and distinguished humanist, was born at Paris Jan. 1, 1760. He studied at the colleges of Du Plessis and Louis-le-Grand, and acquired great proficiency not only in theology, but in medicine, natural sciences, and mathematics. Received as professor in the university in 1789, he entered the Church, and became soon distinguished as a preacher. He was afterwards almoner and librarian of the princess of Lamballe until her murder, Sept. 1792. He then fled to Sceaux, where, under the name of Pastel, he practiced medicine for some time to avoid persecution. He afterwards removed to Meaux, and in 1798 to Paris. Some time after he became connected with the abbot de Fontenay in the publication of the Journal general de Literature, des Sciences et des Arts. After the restoration of Roman Catholic worship he became honorary canon and librarian of the cathedral of Paris, then professor of rhetoric and homiletics in the theological faculty, and almoner of the college of Louis-le-Grand. He was afterward successively appointed almoner of the duchess of Orleans in 1818, and inspector of the academy. His ready acquiescence in the Revolution of 1830 excited the displeasure of the clergy, and it was with great difficulty the king succeeded in obtaining his appointment as bishop of Beauvais. In this position he attended the last moments of the abbe Gregoire (q.v.), to whom he administered the sacraments. Severely censured for this, he referred the matter to the pope, resigning his bishopric in the mean time. Thanks to ,the interference of the court, the matter was settled, and Guillon was appointed bishop of Morocco in parti-bus infidelium, July 7,1833. In 1837 he was appointed dean of the faculty of theology; but, when the French government and the clergy entered into closer union, Guillon was sacrificed by being sent to Dreux to keep the chapel which had successively received the remains of several children of the king. He died in Montfermeil Oct. 16, 1847. He was a most prolific writer. Among his theological works we notice the following: Qu'est-ce done que le pape par un pretre (Paris, 1789, 8vo): — Collection eccles., ou refueil complet des ouvrages faits depuis l'ouverture des etats generaux relativement au clerge (Paris, 1791-1792, 7 vols. 8vo, under the name of Barruel): — Parallele des Revolutions sons le rapport des heresies qui out desole l'Eglise (Paris, 1791, 8vo; often reprinted): — Brefs et instructions du saint-siege relatifs a la Revolution francaise, etc. (Paris, 1799, 2 vols. 8vo): — Discours prononce dans l'eglise de St. Sulpice sur l' autorite de l'Eglise romaine (Paris, 1802, 8vo): Hist. generale de la Philosophie ancienne et mo-derne, etc.; ou supplement a la Bibliotheque choisie des Peres grecs et latins (Paris, 1835, 2 vols. 8vo, and 4 vols. 12mo; 1848, 4 vols. 12mo); Hist. de la nouvelle Heresie du xix"ne siecle, ou refutation des ouvrages de M. l' abbe de La Mennais (Paris, 1835, 3 vols. 8vo): Comparaison de la methode des Peres avec celle des predicateurs du xix .... siecle (Paris, 1837, 8vo): — Ouvres completes de St. Cyprien (transl., with a life of the saint, and notes; Paris, 1837, 2 vols. 8vo): — Examen critique des doctrines de Gibbon, du docteur Strauss et de M. Salvador, etc. (Paris, 1841, 8vo). See Leon Lava, Notice biog. (Moniteur of Dec. 15, 1847); Hoefer, Nouv. Biog. Generale, 22:736 sq.