Leclerc, Sébastien

Title Traité de geometrie
Imprint Paris, J. Jombert, 1690
Localisation Paris, BINHA, 12 RES 527
Subject Geometry
Transcribed version of the text


           From a very early age, Sébastien Leclerc developed a double liking for the sciences and the arts. He took as much interest in drawing and engraving (which guaranteed and still guarantees his fame) as in mathematics, physics, architecture, perspective and fortifications. When he arrived in Paris in 1665 he hesitated between a career in military engineering which he had begun as engineer-geographer with Maréchal de la Ferté and a career as draftsman-engraver. Leclerc’s encounter with Le Brun, First Painter of the King, who followed up by giving him support, persuaded him to choose the second course of action. Since the Edict of Saint-Jean-de-Luz of May 26, 1660, engraving was legally considered to be an independent art; nevertheless engravers found it difficult to escape from the stranglehold of the mechanical arts which had previously confined them. But the practice of perspective and its theoretical justification naturally join together the art of drafting and geometry, a major liberal art. Thus Bosse and Leclerc used mathematics out of sincere liking but also in order to justify their ambition.
           Leclerc, already appreciated as a talented engraver, saw his fame increase after the Pratique de la géométrie sur le papier et sur le terrain came out in 1669. In August 1672 he was taken in as a member of the Royal Academy of Painting and Sculpture which Le Brun directed. Leclerc had the responsibility of teaching perspective and geometry there for 19 years. He was not entirely satisfied with the fame surrounding the Petite géométrie in France and in Europe because its success came mainly due to the admirable vignettes which illustrated it, and quite simply accompanied each page of mathematical text. His treatise was certainly superior to a collection of workshop formulae, but far from the great geometric texts of that period in full scientific effervescence. Therefore, in 1690, 21 years after his first success, he undertook to rewrite a more austere, more theoretical treatise on geometry.
           The frontispiece consists of Geometry holding a compass in one hand and with the help of Mars, standing, holding with the other a shield bearing the lizards and stars of the Le Tellier coat of arms. Even more explicit, a large open book is displayed behind Geometry, leaning up against the pedestal of a column displaying the dedication: “À Monseigneur, Monseigneur le Marquis de Louvois”, with the list of the titles of Colbert’s successor. The treatise is divided in ten chapters. For the first nine, (pp. 1-216), Leclerc presents a succession of propositions of Euclidian geometry in an organized and rational way. A proposition is generally followed by a construction, accompanied by a figure placed in the text, a woodcut, with no ornamentation. The proposition is completed by a demonstration with supporting arguments, which makes all the difference between the Grande and the Petite géometrie. The exposé is thus more thorough but the propositions taken up hardly reach the level of Euclid’s Elements. In chapter VIII he uses trigonometry for the resolution of triangles and takes up the use of algorithms, (p. 179). In this chapter he shows that classical constructions of the regular heptagon and the enneagon are inexact and he calculates their estimation. On the other hand, the last chapter, X, slightly revives the aesthetics of the Petite géométrie. It contains 16 plates containing 45 explanatory figures, sometimes with small people and pleasant landscapes. It is a chapter on “geometry in the situation” in which Sébastien Leclerc deals successively with the use of the guiding line, the surveyor’s graphometer, the sector and the plane table.
           In 1744 Charles-Antoine Jombert had the idea of having the woodcuts of all the figures in Jean Jombert’s edition engraved in copper-plate and adding “at the bottom of each plate little grotesques, drawn and engraved by themost celebrated engravers”, as it happened, Charles-Nicolas Cochin junior and Pierre-Quentin Chedel. Thus Jombert published the Traité de géométrie théorique et pratique à l’usage des artistes par Sébastien le Clerc which, 50 years after Leclerc’s treatise, created a synthesis between the Petite and the Grande géométrie, in fact producing excellence between Mathematics and Fine Arts.

Jean-Pierre Manceau (Tours) – 2016

Critical bibliography

C.-A. Jombert. Catalogue raisonné de l’œuvre de Sébastien Le Clerc..., vol. 1, vol. 2, Paris, C.-A. Jombert, 1774.

P.-J. Mariette, Abecedario et autres notes inédites de cet amateur sur les arts et les artistes. Ouvrage publié... et annoté par... Ph. de Chennevières et A. de Montaiglon, Paris. J.-B. Dumoulin, 1856, vol. 3, pp. 97-112.

E. Meaume, 1637-1714 Sébastien Le Clerc et son œuvre gravé, Paris, Baur & Rapilly, 1877.

M. Préaud, Inventaire du fonds français. Graveurs du XVIIe siècle, Sébastien Leclerc,vol. 8.1; vol. 9.2, Paris, Bibliothèque nationale, 1980.

Sébastien Le Clerc, 1637-1714 [Catalogue of the exhibition organized by the Bibliothèque municipale de Metz, May 27-July 26, 1980], Metz, Bibliothèque municipale de Metz, 1980.