Nouvelles expériences sur la Résistance des Fluides

Charles Bossut, Jean D’Alembert, 1777

Charles Bossut (1730-1814) was a French mathematician Jesuit acknowledged as an expert on hydraulics and hydrostatics, in which he became one of the main French exponents of the eighteenth century. He was born in Tartaras in 1730, a village in the south of France. He studied at the High School Ampere, in Lyon, a Jesuit college where he began to devote himself to scientific research under the guidance of Père Béraud (1702-1777). In 1752, at the age of twenty-two years, he became a professor at the school of military engineering École du Génie at Mézières and collaborated with two brilliant mathematicians of the time: Leohnard Euler (1707 – 1783) and Daniel Bernoulli (1700 – 1782). There, he worked as a professor until 1769 and later as an examiner of students. Bossut was admitted to the Academy of Sciences in Paris as a correspondant in 1753.

In 1764, in Paris, Bossut collaborated with G. Viallet, Deputy Inspector of Bridges and Roads for the province of Champagne to publish the treatise Recherches sur la construction la plus avantageuse des digues. In 1771, he published his work Traité élémentaire d'hydrodynamique, based on research carried out over the years at Mezieres.

He was encouraged in his mathematical research by the encyclopedist Jean Baptiste Le Rond D’Alembert (1717 – 1783), who edited the famous Encyclopédie de Diderot et d’Alembert. In this context, he wrote the scientific section of the Encyclopédie méthodique. Also, in collaboration with D’Alembert, he published a treatise entitled Nouvelles experiences sur la resistance des fluids, in 1777.

He was the author of several works crowned by the French Academy of Sciences and his writings became a fundamental basis for the study and teaching of mathematics and some more specialized fields. Bossut was particularly interested in the problems of hydraulics. The importance of Bossut for the history of science is not only due to specialized research in hydraulics, but also to his role as a major contributor to French (and European) scientific education.

In 1775, he was called by the economist and minister of finance of Louis XVI, R. J. Turgot (1727 – 1781) to collaborate, along with D'Alembert and N. Condorcet (1743 – 1794), for a study on canals and natural waterways inland France for a development and improvement of trade. At the time, he was teaching hydrodynamics at the Ecole Royale du Génie in Mézière, but later, thanks to his collaboration with Turgot, a special chair was created at the Louvre in 1774, which he occupied until 1780. It was Turgot himself who created the special chair.

Turgot asked D'Alembert, Condorcet and Bossut to carry out studies to improve navigation within the French territory, with the aim of making trade more efficient. Bossut then carried out, in the summer of 1776, experiments on the basin of the Royal School of Engineering of Mézières to evaluate the resistance experienced by a body in motion within a fluid. The results obtained by Bossut were published in collaboration with D'Alembert and Condorcet the following year, in a treatise entitled Nouvelles expériences sur la résistance des fluids, where were reported the experiments conducted to enhance navigation within the French kingdom.

In 1786 was published by the Imprimerie Royale, the long compendium Traité théorique et expérimental d’hydrodynamique, which included both the contents of Traité élémentaire d'hydrodynamique (1771) and Nouvelles expériences sur la résistance des fluids.

The treatise Nouvelles expériences begins with a Discours preliminaire, which highlights the criticality of some issues of technical-theoretical hydrodynamics and its importance in practical applications, such as the construction of dams, hydraulic machines and naval architecture. In fact, Bossut was not precisely an engineer, but more a mathematician and natural philosopher, he used experimentation primarily as a point of reference for modifying theoretical equations with mathematical elements. The work consists of six chapters, only the fifth of which is divided into four additional sections. The content is highly mathematical and theory and practice combined. The authors propose tables for data collection and discussion, to test the assumptions and laws describing the resistance of indeterminate fluids. The work concludes with a discussion, of theoretical-mathematical nature, by Condorcet: Essai d'une méthode, tour trover les loix des phénomènes apres les observations.

The treatise, precisely the French edition of 1777, is present in the National Library of Portugal (BNP) and the National Library of Spain (BNE).