Abstract In the second half of the 19th century, among his many other activities, French scholar Gustave Le Bon built his career by giving lectures illustrated with optical lantern slides. He pursued what could be called a “cross-media strategy” to promote his work. He combined public lectures and publications on a variety of subjects, theoretical studies as well as handbooks. He was clearly business-oriented, and marketed not only his books but also lantern slides and even apparatuses. After his first illustrated lectures in the early 1870s, Le Bon developed a photographic method for location surveys and applied chronophotography to the training of horses while continuing his lecturing activities. This article aims to reconstruct Le Bon's specific “scientific persona” in this first period of his career and analyse the fundamental role played by his engagement with optical media, in particular photography. It will argue that both his cross-media strategy in science popularisation and his engagement with the medium of photography made it possible for him to acquire a position outside academic institutions as a central figure in the French intellectual landscape of the late 19th and early 20th centuries.

When documenting historical cases, one must decide which historical actors will be included in the narrative. These choices are connected to the researcher's intentions, which, in turn, are based on the chosen sources and contributions. With these premises in mind, this study examines the historical case of the record of the 1919 total solar eclipse in Sobral, Ceará, Brazil. The measurements taken during this eclipse significantly contributed to the widespread recognition of Einstein and his theories. This paper analyzes primary sources that reported the eclipse observation, such as reports, letters, and local newspaper articles, to identify social actors who participated in the scientific practice. The results indicate that the names of some Brazilian workers who made significant contributions and operated as problem-solvers were not recorded in the official documentation, making them historically invisible. It is impossible to identify their names, faces, or the details of the work they performed. This study indicates that the invisibility of those Brazilian social actors engaged in the Sobral eclipse was probably related to their race, class, and gender, which are important factors in the (in)visibility of certain groups of social actors in science and in the history of science.

Centaurus 66. 1-2 (2024) Centaurus.Journal of the European Society for the History of Science, is an international English language journal and the official journal of the European Society for the History of Science (ESHS).Centaurus publishes high quality academic content on the history of science in the broadest sense, including the history of mathematics, biomedical sciences, earth sciences, social sciences, humanities and technology, studied from different perspectives, including epistemic, social, cultural, material and technical aspects.We also invite contributions that build a bridge between history of science and other disciplines.There are several types of manuscripts, including original research articles and historiographical articles.

Abstract We generally assume that the encounter with the Americas contributed to the downfall of trust in the ancient authorities. Not only did the ancients have no specific knowledge of the existence of the so-called “New World,” but the knowledge they did possess proved, in some cases, to be contradictory to the new discoveries. One of the main fields in which experience of the New World was used to criticise ancient knowledge was meteorology, and in particular the fact that the torrid zone was not extremely hot and dry as the ancients had claimed, but of a pleasant climate with abundant vegetation. This paper investigates how Juan de Cárdenas (1563–1609) made use of his experience in the New World to support the truth of Aristotle's theories in the field of meteorology. More precisely, Cárdenas employed the hypothesis of subterranean caves to account for the humidity and pleasant climate of the West Indies in the tropics. In this way, he claimed that this new land was exceptional, while he sought to preserve Aristotle's theory that the torrid zone, in normal conditions, is indeed dry and hot. Cárdenas aimed to prove that the peculiarities of the New World can only be explained by his hypothesis, and he used a comparison between Spanish and American vegetation to show why the former is the result of a perfect nature, while the latter is inferior due to its location on top of these caves, which do not allow nature to follow its own course, which in this case would be complete dryness and lack of vegetation.

Abstract In the 1750s the Russian academician and chemist Mikhail Vasil'evich Lomonosov experimented with making coloured glass in his laboratory at the Imperial Academy of Sciences in St. Petersburg. Lomonosov went on to open a manufactory nearby at Ust-Ruditsa, where he produced coloured glass mosaics. This enterprise has been represented variously as the work of a lone genius, as a failed business enterprise, and more recently as a form of projecting. The present essay places Lomonosov's glass work in a courtly context, as in part a continuation of the Academy's role of celebrating the Russian sovereign through spectacles such as fireworks and illuminations. Lomonosov sought to shape and contribute to a “ruling image” for the empress Elizabeth Petrovna, turning to mosaics owing to their capacity to interweave Russian tradition, Orthodox religion, and enlightened chemistry. Glass was a business, to be sure, but also a courtly, political, and religious material in Lomonosov's experiments.