Polar motion measurement at the Observatoire de Lyon in the late nineteenth century

The motion of geographic poles, predicted by Euler, was discovered at the end of the 1880s, mainly by German and American astronomers. However, French astronomers were strongly reluctant to accept the reality of this phenomenon. Indeed, all observations at the Observatoire de Paris converged toward non-detection of the polar motion. Science, as most fields of public life, was extremely centralized in France, and the Observatoire de Paris was still living on past glory gained in the field of classical astronomy. However, the directors who succeeded Urbain Le Verrier were doubtful about the accuracy of the observation in such an urban observatory, and were pushing for the construction of an observatory outside the city. At the same time, just after the French defeat of 1871, a wide decentralization of the universities started, and a few big regional cities were selected to host new observatories. In this paper we show how it is in one of these new observatories, in Lyon, that the polar motion was first observed in France, and how this was immediately recognized internationally. Although the weight of French Jacobinism kept the new observatories at an embryonic stage for many decades, this contribution to an internationally discussed problem shows how enthusiastically and efficiently work was carried out in the early years of French provincial observatories.