This article, drawing on ethnographic study in a chemical physics research facility, explores how notebooks are used and produced in the conduct of laboratory science. Data include written field notes of laboratory activity; visual documentation of "in situ" writing processes; analysis of inscriptions, texts, and material artifacts produced in the laboratory and assembled in notebooks; and an in-depth interview with an expert chemist whose research and writing formed the basis of this investigation. Findings from this study suggest that the notebook occupies a negotiated space between the scientist's contingent response to exigency in the laboratory and the genre-specific strategies that he or she deploys to communicate his or her work outside the laboratory. This text, the author argues, might therefore be understood as a "locus" in the sense that it facilitates a reflexive process whereby inscriptions are used both to interpret a-perceptual chemical phenomena in time, and, through their inclusion and integration in the notebook, to discipline that interpretation over time. Tracing the way inscriptions move between material synthesis, on the one hand, and text production, on the other, this article ultimately offers a methodical approach for investigating how the material, technical, and symbolic dimensions of writing and text converge in a modern scientific workplace. (Contains 7 figures, 3 tables, and 7 notes.)