AMBROISE FIRMIN DIDOT (1790-1876), was the eldest son of the preceding. After receiving a classical eclucatioa, lie spent three years in Greece and in the East; and on the retirement of his father in 1827 he undertook, in con-junction with his brother Hyacinthe, the direction of the publishing business. Their greatest undertaking w as a new edition of the Thesaurus Grcecce kingutz uf Henry Stephens, under the editorial care of the brothera Dinclorf and M. Hase (9 vols. 1855–,59). Among the numerous important works published by the brothers, the 200 volumes forming the Bibliotheoue des auteurs theque latine, and Bibliothegue francaise deserve special mention. Ambroise Firmin Didot was the first to prepose (1823) a subscription in favour of the Greeka, then in insurrection against Turkish tyranny. Besides a trans-lation of Thucydides (1833), he wrote the articles " Estienne " in the Nouvelle Biographie Generale, and " Typographie " in the Riley. Mod., as well as Observa-tions SW' l'orthographie francaise (1867), S.:c. In 1875 he published a very learned and elaborate mono,grapli e Aldus Manutius. His collection of MSS., the richest' in France, was said to be worth, at the time of his death, not less than 2,000,000 francs.