In 1942 I was in a class at the lycée Saint-Louis with Jean-Claude Pecker. On 7 June, some of our comrades, including Pecker, arrived at the school with a yellow star. Pecker and I passed the written and then the oral entrance examination to the École Normale Supérieure. The oral ended for the candidates of the occupied zone on 14 July 1942. Pecker immediately tore off his yellow star and the next morning, we left both from Saint-Lazare station for Saint-Germain. We went camping on the land of a brave farmer whose address Pecker had. On 16 July, the French police arrested all Jews in the Paris region and brought them together at the Vélodrome d'Hiver before sending them to Drancy and then to Germany. After a week, the roundup being over, we returned and Pecker went to an unoccupied zone where he lived under a false name.

... during my stay in Britain, I wrote an article on the application of continued fractions to the formation of transcendental numbers; the relations between France and England being restored, I sent this article to my father, who submitted it to the "Revue Scientifique", in which it was published.

In the Air Force, first in Morocco, but especially in England in the Royal Air Force, I had seen the very important progress made in aviation and aeronautics. Fortunately the Germans had failed to realise the importance of the atomic bomb, but in the field of aeronautics they surpassed the Allies. As early as 1944, they had built the flying bombs, the V1s, which I saw coming crashing down on London, then the V2s, which I heard crashing on London. The Messerschmitt factories in Augsburg had made the first jet planes, which were used at the beginning of 1945. There was already talk of supersonic flights, and the year 2000 was scheduled for landing on the moon. I thought that by working in fluid mechanics, I would participate in the progress of aeronautics and I asked Joseph Pérès to direct my research and my first thesis. Pérès told me that since 1939, France had continued in the study of incompressible fluids, which was sufficient when planes were flying at 300 kilometres an hour, but had become insufficient, especially for the future. He therefore advised me to study the German works on the subject and to make a thesis. At the time I had not yet forgotten the German language, which I had learned in high school, and the French had recovered the maximum number of documents in their zone of occupation in Germany and Austria. The aeronautical documents were entrusted to the Office National d'Etudes et de Recherches Aérospatiales (O.N.E.R.A.), the National Office for Aeronautical Studies and Research, which met at regular intervals with German engineers housed in a hotel. I was invited to these meetings; I was a beginner on the subject and later realized that many of the questions I asked were quite naive. But, following Pérès very judicious advice, on 5 February 1950, I submitted the doctoral thesis 'Contribution a l'étude théorique des fluides compressibles. Écoulements transsoniques. Ondes de choc' Ⓣ. What a difference from the way that theses are done today, where thesis advisors feed their students with a teaspoon!

In 1948, a classmate, Madeleine Lebon, and I got married. At the time the two schools Ulm and Sèvres were separated, but promotional outings were an opportunity to get to know each other and were at the origin of several marriages.

Madeleine had passed the scientific competitive exam, but once at the École Normale Supérieure she had decided to follow studies in philosophy, which was allowed by the rules. She hence did what I had considered and that brought us closer. Madeleine Lebon was a full believer, brought up in a practicing Catholic family where she was happy. She was also very close to her brother and sister. "I have never doubted", she told me one day. My mother pointed out to me that that assertion is not very compatible with the profession of philosopher. Madeleine was, however, a very intelligent woman who had passed, with "very good", both the scientific and literary baccalaureate, a feat I had not managed. As the Aggregation of philosophy did not offer many positions, she had not been admitted to it. She had considered a re-conversion to mathematics - my entire class had been successful at the competitive exam - when marriage and children convinced her to remain a housewife.

I had been happy to find, in Marseille, my friends Henri and Madeleine Cabannes. Madeleine was always optimistic, persuaded of the goodness of God in spite of the problems caused by her second son who, she told me, was not "well come". The baby Jean-Paul did not tolerate any dairy product, except Roquefort. The courage and perseverance of Madeleine ensured his survival. In fact Jean-Paul was what was then called a mongoloid. In 1953, the chromosomal origin of this handicap, trisomy twenty-one, was not known. Madeleine spent considerable energy on her son, thinking that assiduous material and intellectual care would make him an ordinary man. She even took him for a Bogomoletz treatment, and persevered in her hope in spite of its failure. Unfortunately, Jean-Paul was a severe case. It is now known that the severity of the harmful effects due to the supernumerary chromosome 21 depends on the location where it is attached to the other two. To her deep regret, pushed by her husband, Madeleine had to resign herself to placing the adolescent Jean-Paul in an appropriate facility in the interest of her other four children, all "well come".

The Cabannes already had, besides the Down syndrome sufferer Jean-Paul, two boys: Jean-Pierre - a few months older than Michelle [Yvonne Choquet-Bruhat's daughter] - and André - a few months younger - and a girl of little more than a year, Hélène. In the fall of 1957, they had a fifth child, a charming baby, Benoît. It was the time of the baby boom. Madeleine, a devout Catholic, would still want other children, but as she had to have surgery for a fibroma, it stopped her pregnancies. Henri was rather glad of that; he said, "Five is good." Madeleine was helped by a very nice girl living at their home, but her baby, the little Hélène and Jean-Paul did not let her be idle. The two elders went to the public school in Saint Cyr, but still demanded a lot of time from their mother. Madeleine came each morning to take Michelle and drive her to school with her sons. Jean-Pierre and André were half-boarders but I picked Michelle up to have lunch together. ... In general, Madeleine went in the afternoon to pick up the children from school.

This excellent text corresponds to the course that the author teaches at the Sorbonne. The contents are best indicated by the following titles of chapters and abbreviated headings of sections.

Part I. General Mechanics: Kinematics (vectors, velocities, accelerations); Kinetics (mass distributions, quantities associated with velocities, quantities associated with accelerations); Principles of mechanics (fundamental law, momentum theorems, search for absolute frames of reference, special theory of relativity); Problem types (statics, dynamics, impact, friction); Work and power (definitions and basic properties, theorem of virtual velocities, units); Differential equations (methods of integration, linear equations, oscillations); Analytical mechanics (Lagrangian equations for holonomic and non-holonomic systems, stability of equilibrium, small oscillations); Rigid bodies (general theory, gyroscopes).

Part II. Introduction to fluid mechanics: Microscopic aspects (concepts of statistical mechanics, hypotheses of kinetic theory, equations of kinetic theory, macroscopic equations); Macroscopic aspects (integral form of equations of motion, equations for continuous motions, equations for discontinuous motions).

The presentation has the clarity that is a characteristic of French texts in this field; vector and tensor equations are used wherever this is advantageous.

The scientific work of Henri Cabannes revolved around various topics. Each theme occupied him exhaustively for periods of five to ten years, where personally he worked hard, while increasing contacts and collaborations in France and abroad, and supervising young researchers, who often pursued the area once he had opened the next.
Topics:
1. Aerodynamics. Shockwaves attached and detached from obstacles.
2. Magnetodynamics of fluids.
3. Kinetic theory of gases. Determination of viscosity and conductivity from particle kinetics. 4. Discrete kinetic theory. Existence of solutions.
5. Vibrating ropes with obstacle or solid friction. Periodic and near-periodic solutions.