Academic careers in French science during the mid-nineteenth century were made within the Université de France, an integrated state system of secondary and higher education controlled by a centralized Parisian educational administration. Among the most respected members of the corps universitaire were Charles d'Almeida and Pierre Bertin, two historically obscure physiciens whose significance derives from their substantial contributions to the social organization, teaching and communication of French experimental physics. This two-part comparative biography uses their entwined careers to make a case for the emergence of a discipline of French experimental physics from the corps during the tumultuous politico-cultural transition from the Second Empire to the Third Republic. Of fundamental importance are disciplinary regimes of teaching and inspection within the corps, the foundation of the Société française de physique and the Journal de physique, and the diversification of the traditional pedagogical role of the Ecole normale supérieure, which, from around 1860, began to offer a career pathway for aspiring scientific researchers. Having established in this paper the socio-institutional mechanisms for the stabilization of a distinct field, in part two I characterize the epistemological–methodological aspects of French experimental physics.