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John Tyndall, FRS (1820-1893), the eminent scientist and mountaineer, the discoverer of the greenhouse gases, has been frequently presented as chiefly a populariser of science rather than a researcher. Although he regarded this education as an important function to fulfil, his researches and discoveries reported in the publications of the Royal Society, the Royal Institution and the British Association for the Advancement of Science, constitute a testimony to his standing as a scientist, hitherto neglected by his commentators. This thesis studies his contributions to the physics of the atmosphere and their subsequent impact on meteorology, research that is relevant to today’s concerns about climate change. Tyndall, did however, also make discoveries in other branches of physics, chemistry and bacteriology. Like many aspiring British scientists of the nineteenth century, Tyndall went to Germany as a mature student. He chose the University of Marburg to study chemistry, physics and mathematics under the renowned chemist, Robert Bunsen, the physicist Gerling and the mathematician Stegmann respectively, graduating with a PhD in applied mathematics. [1] At this time Faraday’s extraordinary discovery of diamagnetism in 1846 were causing a sensation in Germany, France and Britain. Scientists eagerly studied Faraday’s research, replicating his experiments and interpreting his findings. Faraday’s work apparently confirmed concomitant researches by Plücker on the magnetic properties of crystals. Tyndall’s pioneering contributions to the study of diamagnetism [2] constituted his formative experiences as an experimentalist. He effectively challenged the opinions of the distinguished scientists, Faraday and Plücker. [3] The deportment of magnetism with respect to matter provided Tyndall with a comprehensive alternative to Faraday’s views on the interaction of point forces with matter. Tyndall’s analogous investigation of radiant heat and its transmission by the atmosphere enabled him to study matter in its gaseous phase, hitherto inaccessible to the experimental process, and to participate in the all-important shaping of meteorology as a scientific discipline. The analogous interactions of matter with the forces of light and heat prompted Tyndall’s speculations on the role of the molecular structure in the modification and transmission of forces. The Tyndall Centre for the Study of Climate Change, thus named in his honour in the year 2000 by the Director of the Royal Institution, Professor Peter Day, testifies to the importance of Tyndall’s contributions to the all pervading problems which today face mankind. This thesis also addresses his role as a leading publicist for scientific naturalism and campaigner for science education, throwing a new light on his motives. On the death of his mentor and friend, Faraday, Tyndall succeeded him as Resident Professor in charge of the Royal Institution. In this historic laboratory Tyndall devised and perfected experimental methodology for the study of matter in its gaseous phase, thought, until then to not be amenable to scientific investigation. The importance of this contribution to science, underestimated over the years, is highlighted in the thesis. The thesis also looks at his pioneering researches on gases through their interaction with radiant heat and light. It examines how he used the forces of nature as tools to probe the nature of matter. It presents one consequence of Tyndall’s work that led to the discovery of calorescence, from a new perspective. The author of over 100 scientific papers, Tyndall is revealed as an inspiring research scientist, honoured by the Royal Society and numerous foreign academies. He was however castigated for an inadequate knowledge of mathematics, because he concentrated on imaginative physical interpretations of theoretical notions. At times, therefore, he was seriously underestimated as a scientist, despite admiration by some for the excellence of his work. This theme is also analysed in the thesis. Emerging from this study is an image of Tyndall’s serious engagement with science, and his role as an eminent practitioner and spokesman, who viewed science as beneficial to mankind, and physics as a means of education. 1 Tyndall (1870). 2 Tyndall (1851) 2, (9), 165-188. 3 Plücker (1849), 5, 353-375; 376-382.

Unique français parmi les fondateurs de la mécanique quantique, Louis de Broglie est une figuremajeure de l’histoire de la physique française du XXème siècle. Il devient grâce à son prix Nobel dephysique en 1929 le personnage central de la physique théorique française. Dans les récits usuelsportant sur la physique française du XXème siècle, la mécanique quantique est décrite comme s’étanttrès lentement diffusée en France, et il est souvent admis que peu de physiciens de ce pays l’utilisèrentavant la fin de la seconde guerre. De Broglie est souvent désigné comme le grand responsable de cetétat de fait et est dépeint comme un représentant type d’une pratique de physique théorique obsolète.De plus, son rôle institutionnel et sa responsabilité dans l’isolationnisme français sont dénoncés.Le but de ce travail est, premièrement, d’éclairer les modalités de la diffusion de la mécaniquequantique en France et le rôle de Louis de Broglie dans ce processus. Ce faisant, mon propos apporterade fortes nuances aux habituels récits portant sur cet aspect de l’histoire de la physique française duXXème siècle. Deuxièmement, je montrerai que l’essor de domaines tels que la physique des particules,la physique du solide et la physique nucléaire après la seconde guerre mondiale introduit unchangement dans les pratiques des jeunes théoriciens par rapport aux pratiques qui régnaient autour deLouis de Broglie. Je serai alors en mesure d’expliquer pourquoi l’héritage de Louis de Broglie au seinde la physique française de la seconde moitié du XXème siècle est si peu revendiqué, tout en évitant detomber dans le piège des jugements rétrospectifs et péjoratifs. / As the only Frenchman among the founding fathers of quantum mechanics, Louis de Broglie has agreat importance in the XXth French physics. With the prestige from the Nobel Prize in 1929, deBroglie became the main characters of the French theoretical physics community since the 30’s andgreat responsibilities on its evolution were entrusted to him. In the usually story of the XXth Frenchphysics, quantum mechanics, which is the core of theoretical physics since 1925, is said to have spreadslowly in France and French theorists who really used it were few before WWII. This story goes on,saying that de Broglie was the principal guilty of this state of fact. In this story, the discoverer ofwave-particle duality of matters becomes a representative of old-fashioned theorists who practice anaive kind of picture-based physics. Furthermore, his institutional action and his responsibility in theisolation of French physics are stigmatized.The aim of this work is, firstly, to throw light on the modality of the diffusion of quantummechanics in France and the role of de Broglie in this process, both on the intellectual and theinstitutional side. Secondly, it will be shown that progress in the area of particle physics, solid statephysics and nuclear physics after WWII introduce a shift in the practice of many young theoristsrelative to the way of practice theoretical physical inside de Broglie’s group. We will thus be able tounderstand why the legacy of Louis de Broglie is not claimed in contemporary French theoreticalphysics without falling into the trap of a retrospective and pejorative assessment of the career of themost famous French theorist of the XXth century.