LAMM.; PIII IPI'E DE, was born at Paris March 18th, 1640, in which city he also died April 21st, 1719. Up to the ago of twenty four years he followed the profession of his father, who had acquired considerable reputation as a prefer/en of painting and sculpture to the Royal Academy. In 1660 he visited Italy, partly for the improvement of his health, and partly with a view to the completion of his pro.
fessional education. While at Venice he applied himself to the study of geometry, and morn particularly to the conio sections of Apollo mites ; and a few years after his return to Para he published several treatises upon those subjects, which fully established his claim to the reputation of a profound geometrician. In 1679, Culbert having slug.
gesieel the construction of a general map of France, I'ieard aud De Lahire were nominated by the king to conduct certain surveys along the coast of Gascony, and in 1683, Do Lahire, in conjunction with Dominic Cassini, was instructed to proceed with the ineounirement of the meridian, which bad been commenced in 1669 by Picard. [PICAItD.] The death of M. Colbert having put a stop to this import ant undertaking, he was next employed in determining the difference of level of the river Eure and the reservoir of Versailles, preparatory to the construction of an aqueduct for the supply of the capital, which he affected to the satisfaction of the king, and of Louvoie, the then minister. The other publio works in which M. Do Lahire was suc cessively engaged were numerous and important, but our limits will not permit us to notice them more particularly. Ito was twice married,
and "each of his marriages," says M. Fontenelle, "furnished an Academician." Although he does not appear to have been altogether unacquaiuted with the influitesimel calculus, the whole of the subjects upon which he has written are treated synthetically. In his manners be was more reserved than the geuciality of his countrymen, but the uprightness and disinteresteduess of his conduct were most exemplary. A pure piety, free from superstition and singularity, characterised the whole of his life.
For further information the reader may advantageously consult the Ill6moires do Niceiron,' tom. v. and ' l'Histoire du College Royal,' by Goguct; and the Eloge de Lahire,' by Fontenelle (' CEuvres Diverses,' folio, 1729), from which this notice is chiefly drawn. His published works are-' Treatise on Conical and Cylindrical Sections,' Paris, 1673, 4to; 'De Cyeluide Oputiculum,' 1676; 'Conic Sections and Geometrical Loci,' 1679; Gnomonics, or the Art of making Sun dials,' 1682; Conic Sections,' 1685, folio; Tnlinthe Astronomicre,' 1702, 4to ; Treatise on Surveying,' 1689 ; Mechanics,' 1675 ; Description of the Globes in the Pavilion of the ChAteau do Marli; 1704; besides numerous memoirs in the public journals of the day, and more particularly in the' Transactions of the Academy of Sciences,' from 1666 to 1718.