Seeing the Invisible: The Introduction and Development of Electron Microscopy in Britain, 1935–1945

INTRODUCTIONSpring, 1941. The German campaigns in the Balkans are strengthening the Nazi domination of continental Europe. The Lend-Lease bill signed by Roosevelt on 1 1 March has broken any neutrality pretence of the USA. War material is being sold, transferred or leased to the Allied nations in the name of assisting US defence. The war is about to become global and US and British leaders discuss strategy in the event that the USA finally enters actively into the war. In this context, the British physicist Charles Galton Darwin (1887-1962) is appointed Director of the British Central Scientific Office in Washington - an institution conceived to promote closer contact and exchange of information on uranium investigation between US and British scientists.1 Darwin is one of the British scientists involved in the work on an atom bomb project. He spends almost one year in Washington. During this time, he reports to the physicist and member of the Department of Scientific and Industrial Research (DSIR),2 Edward Victor Appleton (1892-1965), on the electron microscope, strongly advocating for the importation of several of these instruments.3 What was this new apparatus? Why was there such an interest in it? Was it expected to help in the war effort at all?This paper explores the introduction of electron microscopy in Britain in the early 1940s. It deals not only with the interest that the electron microscope originally awoke amongst some scholars, but also with the doubts and reluctance shown by several scientists - particularly life scientists - towards its development and potential uses. I contend that the specific context of World War ? was crucial in overcoming these differences, favouring the introduction of the electron microscope in Britain. It was the thread of chemical and biological warfare, together with industrial interests and the prospective uses of the electron microscope to the war effort, that finally made British scientists and policymakers advocate for the importation of several electron microscopes and for the development of electron microscopy in the country.THE EARLY DAYSThe development of the electron microscope in the 1930s had been possible thanks to the improved understanding of cathode ray tubes, together with the progress in techniques for achieving high vacuums. In 1928, Hans Busch (1884-1973) had demonstrated and proved mathematically how coils that generate a magnetic field of rotational symmetry could be used to focus electron beams. Soon after this, work on the development of electron microscopy began in Germany, such as that at the Allgemeine Elektrizitats-Gesellschaft (AEG) under the leadership of the head of the physics laboratories Ernst Bruche (1900-85). However, it was the engineers from the Technische Hochschule of Berlin Max Knoll (1897-1969) andErnst Ruska (1906-88) who in the early 1930s, using some of the methods and apparatus already developed to some extent for the purpose of cathode-ray oscillography, were the pioneers of the construction of an electron microscope in Germany.4The publication of the first results obtained by the Germans, though still very modest, opened the doors for the development of several electron microscope projects in countries such as the USA, Canada, Belgium, and Great Britain. A good example is that of Ladislaus Marton (1901-79), a physical chemist at the Free University of Brussels and one of the pioneers not only of electron microscopy, but also of the application of electron microscopy to biomedical studies. In fact, he was one of the individuals involved in the development of electron microscopy both in Belgium and America, where the Radio Corporation of America Company (RCA) was to play a crucial role.It was not Marton but James Hillier (191 5-2007), a postgraduate student who was building an electron microscope for his doctoral research in physics at the University of Toronto, who produced the first commercial American electron microscope for the RCA in February 1940 - just a few months after the German firm Siemens had offered the first commercial model. …

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