HACHETTE, JEAN NICOLAS PIERRE (1769-1834), an eminent French mathematician, was born at Mezieres, where his father was a bookseller, on the 6th May 1769. For his early education he proceeded first to the college of Charleville, and afterwards to that of Rheims. In 1788 he returned to Mezieres, where he was attached to the school of engineering as draughtsman to the professors of physics and chemistry. When twenty-three years of age he succeeded from among a number of candidates in gaining the professorship of hydrography at Collioure and Port-Vendre. While there he sent several able papers, in which some questions of navigation were treated geometrically, to Monge, at that time minister of marine, through whose influence he obtained an appointment in Paris. Thence he passed to a deputy-professorship, at Mezieres, and towards the close of 1794, when the Ecole Polytechnique was established, he was chosen one of its staff, being appointed along with Monge over the department of descriptive geometry. There he instructed some of the ablest Frenchmen of the day, among them Poisson, Aram:), and Fresnel. Accompanying Guyton de Morveau in his expedition, earlier in the year, he was present at the battle of Fleurus, and entered Brussels with the French army. In 1816, on the accession of Louis XVIII., he was expelled from his chair by Government, at the same time that his friend and fellow-worker Monge was removed from the Institute. He retained, however, till his death the office of professor in the faculty of sciences in the Ecole Normale, to which he had been appointed in 1810 - the same year in which he married the daughter of the physician Maugras. The necessary royal assent was in 1823 refused to the election of Hachette to the Academy of Sciences, and it was not till 1831, after the Revolution, that he obtained that well-merited honour. He died at Paris, January 16, 1834. Hachette was held in high esteem for his private worth, as well as for his scientific attainments and great public services. His labours were chiefly in the field of descriptive geometry, with its application to the arts and mechanical engineering. It was left to him to develop the geometry of Monge, and to him also is due in great measure the rapid advancement which France made soon after the establishment of the Ecole Polytechnique in the construction of machinery. His writings on descriptive geometry are still of value.

ILuhette's principal works are his Deux Supplements a in Geometric Descriptive de Mongc, 1811 and 1818 ; Elements de Geometric a trois dimensions, 1817 ; Collection des Epures de Geometric, &c., 1795 and 1817 ; Applications de Geometric Descriptive, 1817 ; Thrill de Geometric Descriptive, 8:e., 1822 ; Traite Elementaire des Machines, 1811 ; Correspondence sar l'Eeole Polytechnigne, 18041815. He also contributed many valuable papers to the leading scientific journals of his time.

H HETTE, Lours CHRISTOPHE FRANCOIS (18001861), a French publisher, was born at Rethel in the Ardennes, May 5, 1800. After studying three years at a normal. school with the view of becoming a teacher, he was in 1822 on political grounds expelled from the seminary. He then devoted several years to the study of jurisprudence ; but in 1826 he resolved to establish in Paris a publishing business, the main object of which should be the issue of works adapted to improve the system of school instruction, or to promote the general culture of the community. The series of works which from that time were brought out by him included manuals in various departments of knowledge, dictionaries of modern and ancient languages, educational journals, and French, Latin, and Greek classics annotated with great care by the most eminent authorities. Subsequent to 1850 he, in conjunction with other partners, published a cheap railway library, scientific and miscellaneous libraries, an illustrated library for the young, libraries of ancient literature, of modern foreign literature, and of modern foreign romance, a series of guide-books, and a series of dictionaries of universal reference. In 1855 he also founded Lc Journal pour tons, a publication with a circulation of 150,000 weekly. There can be no question that by his efforts to circulate such a variety of wholesome and instructive literature, Hachette is entitled to rank among the greatest benefactors of his country. He also manifested great interest in the formation of mutual friendly societies among the working classes, in the establishment of benevolent institutions, and in other questions relating to the amelioration of the poor, on which subjects he wrote various pamphlets ; and lie lent the weight of his influence towards a just settlement of the question of international literary copyright. lie died 31st July 1861.