1 This is a preliminary, unpublished version (pre-print) of a book chapter. It may be used and cited according to the description presented below, informing the corresponding link and the date you accessed the work. MARTINS, Roberto de Andrade. An appreciation of Louis-René Matout, Becquerel’s assistant. Pre-print, June 2022. Available at: https://doi.org/10.5281/zenodo.6615009 However, if you are willing to cite this work, it is advisible to check whether the final version of the same is available. To see whether the work has already been printed, in order to use the final version, with the formatting and pagination that were used in publication, you just have to click the above link. AN APPRECIATION OF LOUIS-RENÉ MATOUT, BECQUEREL’S ASSISTANT Roberto de Andrade Martins Abstract: Louis-René Matout (1869-1944) was a French researcher who worked both with Henri Becquerel (1852-1908) and his son Jean Becquerel (1878-1953) at the National History Museum, in Paris. Initially as a préparateur of the Physics laboratory, afterwards as an assistant, for almost 40 years he participated in the researches developed at the Museum. Besides aiding the investigations led by Henri and Jean Becquerel, he also had an independent scientific production and he became a well-known physicist, in the early twentieth century. This article offers a view of his career, also discussing the claim that he participated in the discovery of radioactivity. Keywords: history of physics; history of science; Henri Becquerel; Jean Becquerel; Louis-René Matout; radioactivity 1. INTRODUCTION The usual approach in history of science gives a lot of attention to the most famous researchers, paying little tribute to the multitude of lesser-known scientists, whose contributions are nevertheless highly relevant. Especially in the case of experimental investigations, a research is seldom an individual activity – it is customarily a group undertaking. This is true today and it was also so one hundred years ago. This article will spotlight one among many unknown research assistants of the early twentieth century: Louis-René Matout (1869-1944), a French researcher who worked both with Henri Becquerel (1852-1908) and his son Jean Becquerel (1878-1953) at the National History Museum, in Paris. Operating in the shadow of two well-known physicists, mostly viewed as a mere supporter of the researches of the two professors, Louis Matout was nevertheless a capable scientist. He began his career at the Paris Muséum d’Histoire Naturelle as a préparateur – a position that is usually construed as a humble technical work, but that was much more than that. In principle, he could progress from préparateur to assistant, and then from assistant to professor of the chair of Applied Physics at the Muséum. He became indeed an assistant, but his career could not proceed further because Jean Becquerel stood on his path. Louis Matout first aided the investigations led by Henri Becquerel from the late nineteenth century up to his death, in 1908, and afterwards he became the assistant of Jean Becquerel. Besides that, he also had an independent scientific production and published many independent papers and two books on physics. He was also the coauthor of some of Jean Becquerel’s