This paper compares the argumentative practices of the English and French scientific communities from the origin of the scientific journal in 1665 up to 1700. To that end, we ask a uniform set of questions related to argumentative practice in a large sample of articles randomly drawn from the three pre-eminent scientific journals of this period: Philosophical Transactions of the Royal Society of London, Journal des Sçavans and Mémoires de l'Académie Royale des Sciences. The results suggest an interesting link between socio-political structures and their influence on early scientific societies, and the articles in their fledgling publications. In particular, the early professionalization of French science through the Académie Royale led to a heightened emphasis on features familiar in 20th-century practice: quantification, mathematical and mechanical explanations for acquired facts, visual representations of facts and their explanations, and use of observations and experimental results as stepping stones to theory. This social arrangement led as well to a narrower view of what constituted acceptable subject matter. Despite these differences, there are also enough similarities in English and French communicative practices to suggest the beginnings of an international scientific community.