Bélidor, Bernard Forest De

(b Catalonia, Spain, 1697/1698; d. Paris, France, 1761)

mechanics, ballistics, military and civil architecture.

Bélidor’s career belongs to the early stages of engineering mechanics.

When Bélidor was born, his father, Jean-Baptiste Forest de Bélidor, a French officer of dragoons, was on duty in Spain. Both his father and his mother, Marie Hébert, died within five months of his birth, and he was brought up by the family of the widow of his godfather, an artillery officer named de Fossiébourg. Grateful for the family’s protection during his childhood, Bélidor married Fossiébourg’s daughter (or possibly his granddaughter) two years before his own death.

His life mingled the scientific with the military. A flair for practical mathematics secured him a post in the field under Jacques Cassini and Philippe de La Hire in the survey of the meridian from Paris to the English Channel, which they completed in 1718 and published in Cassini’s De la grandeur et de la figure de la terre (1720). Bélidor’s talents came to the attention of the regent, the Duc d’Orléans, who discouraged him from taking holy orders and arranged his appointment as professor of mathematics at the new artillery school at La Fère. In this post he made himself known as an author of textbooks and technical manuals in the 1720’s and 1730’s. After an interval of active duty in Bavaria, Italy, and Belgium during the War of the Austrian Succession, Bélidor settled in Paris with the rank of brigadier, was named chevalier of the Order of Saint Louis, and was elected an associé libre of the Academy of Sciences in 1756.

The book that made his reputation was Nouveau cours de mathématique, a text for artillery cadets and engineers. A second, Le bombardier françois, was for use in combat and contained systematic firing tables. It was with two fuller works, however— La Science des ingénieurs (1729) and Architecture hydraulique (1737–1739)—that Bélidor entered into the science of mechanics proper with a summons to builders to base design and practice on its principles. The first of these treatises was concerned primarily with fortifications, their erection and reduction (the term génie then referred mainly to military and naval enterprises). The second, Architecture hydraulique, embraced civil constructions. The choice of title was a reflection of the actual prominence of problems involving transport. shipbuilding, waterways, water supply, and ornamental fountains. Both books opened with formulations of the principles of mechanics in mathematical terms, in which there was nothing original. The discussion was elementary, for the putative marriage of mathematics to mechanics was a rite more often celebrated than consummated in the early eighteenth century.

Nevertheless, the practical contents of both works proved to be invaluable to architects, builders, and engineers. They amount to rationalized engineering handbooks in which the man in charge of a construction might look up model specifications for a foundation or a cornice, a pediment or an arch; find diagrams he could follow or adapt; and consult job analyses and work plans for dividing and directing the labor. Both works were reprinted so often that the copper plates wore out and had to be reengraved for the final editions, in 1813 and 1819 respectively. Those editions were republished with notes by Navier, who in order to conserve the practical value, found it wiser to correct Bélidor’s theoretical faults by up-to-date annotation than to revise or rewrite. He chose this course despite the immense development, amounting almost to creation of analytical mechanics as a science, that had occurred since Bélidor’s first edition.

In that interval, Bélidor’s writings had instructed innumerable practitioners as well as the first two generations of engineers who were also intrinsically scientists: for example, Lazare Carnot, Coulomb, and Meusnier, followed by Coriolis, Navier, and Poncelet, all of the whom, under the designation “science of machines,” inaugurated engineering mechanics. Bélidor’s influence, therefore, was the reciprocal of what he intended: rather than introducing mathematics into practical construction, he brought the problems of engineering to mechanics.

BIBLIOGRAPHY

1. Original Works. Bélidor’s important writings were Nouveau cours de mathématique à l’usage de l’artillerie et deu génie (Paris, 1725); La science des ingénieurs dans la conduite des travaux de fortification et d’architecture civile (Paris, 1729), also ed. with notes by Louis Navier (Paris, 1813; repub. 1830); Le bombardier françois, ou nouvelle méthode de jetter les bombes avec précision (Paris, 1731); and Architecture hydraulique, ou l’art de conduire, d’elever et de ménager les eaux pour les différens besoins de la vie, 2 vols. (Paris, 1737–1739), also ed. by Navier (Paris, 1819)—the most successful eighteenth-century edition was that published in 5 vols. (Paris, 1739–1790). Bélidor also published two memoirs in the Mémories de l’Académie Rovale des Sciences: “Théorie sur la science des mines propres à la guerre, fondée sur un grand nombre d’expériences” (1756), pp. 1–25; and “Seconde mémorie sur les mines, servant de suite au précédent” (1756), pp. 184–202.

II. Secondary Literature. Bélidor’s éloge by Grandjean de Fouchy is in Histoire de l’Académe Royale des Sciences, année 1761 (Paris, 1763), pp. 167–181. Further biographical tradition is recalled in the introduction to the Navier edition of Architecture hydraulique.

Charles C. Gillispie