While the importance to the history of science publishing of both the Journal des Sçavans and the Philosophical Transactions – respectively considered the first learned journal and the first scientific journal, first appearing two months apart on the cusp of 1665 – has long been acknowledged, the early history of both is surprisingly incomplete. Both are major resources for cultural historians and historians of science, both have had their early issues fully digitized and made freely available online, and yet there have been few attempts to analyse the patterns of editorial activity in either of them. For journals generally supposed to have been instrumental in giving posterity the peer review process, the research article, and the book review, there are important lacunae in accounts of their early history and very little research that seeks to compare them directly. The following paper seeks to begin that work. It will investigate the nature, extent and forms of the two journals’ mutual borrowings; where and whether they were fashioned through consenting editorial exchanges; and explores the significance of those patterns in fashioning contemporary natural-philosophical debates and controversies, as well as establishing the future courses of the learned journal. It aims at a fine-grained examination of an important nexus between English and French natural philosophy in the 17th Century, which has hitherto been drawn only in broad, contrastive brushstrokes, and will argue more generally that close examination of the history and practices of publishing science in the two countries in this period enables us to uncover a much livelier awareness and responsiveness in each community to the other’s work than current historiography generally allows.