Analysis of an unpublished treatise of an 18th century engineer, Antoine d’Alleman (1679-1760)

International audienceMilitary culture has occupied a central place in the constitution of constructive knowledge amongst the French intellectual elite since the beginning of the 17th century. The royal engineers, whose trade is rapidly institutionalized and developing in the 17th and 18th centuries, are important agents and vectors of this complex of practical knowledge backed by geometry, mathematicsand the new physics.Despite the recent scientific advances in structural mechanics and strength of materials, it is mainly the knowledge in geometry and mathematics that are put forth in the military architecture and engineering treatises as fundamental and strategic for the engineer, be they considered as prerequisites for access to the physical sciences, as necessary tools for good design and their infield concretization, or as a reliable training method of rational thinking.Antoine d’Alleman is “Chevalier and citizen” of the city of Carpentras, which at the time was the capital of the Comtat Venaissin. He is a specimen of this generation of architects and engineers, having studied a good number of military and scientific treatises, implementing his knowledge throughout a long career as topographer surveyor and hydraulics engineer in this papal territory, an independent state landlocked in the French kingdom. He designed and conducted in the Comtat important civil engineering works representative of those undertaken in the neighboring French provinces by the Corps of military engineers: roads, dikes, canals, aqueducts and water supply for cities, cartography. He also designed important buildings, hospitals, churches and chapels, at Carpentras and Orange. Besides his professional activity, he undertook the project of writing a treatise of architecture.The review of the mathematical parts of these manuscripts informs us of the relationship that such an engineer could establish between theory and practice: a partial mathematization of the topographer surveyor’s graphical and in-field operations, yielding a reliable foundation to his know-how. Within the limited framework of this paper, we will briefly illustrate how this process unfolds pragmatically, by analyzing a limited number of representative propositions of the Ms1127 manuscript, entitled pompously “The engineer, mathematical works of Mister d’Alleman or introduction to the science of engineering”