Graphical: The History of a Category

Abstract

This dissertation is a cultural and conceptual history of the rise and development of graphical methods in the 19th century physical sciences. It delineates the “graphical” as a particular mode of seeing, manipulating and reasoning about physical phenomena that should be distinguished from the geometrical approaches of the 18th century. The dissertation goes beyond previous studies that have only described the use of graphical methods as a form of discipline or practice. Instead, it reconstructs a “period eye” to explain how historical actors formed patterns and associations by looking at, thinking about or manipulating graphical objects. Through this approach it is shown that the impact of graphical methods went beyond their practical use. The “graphical” provided a rhetorical and intellectual mean of mediating between different social and epistemological constraints such as the workshop and the classroom; abstract theory, empirical rules and experimental data; algebraic equations and geometrical constructions; or conflicting notions of generality and precision. By tracing the use of “graphical” either as a qualifying adjective or a suffix, it is shown how in the late-18th and early-19th century certain operations, constructions, methods, representations or instruments came to be understood, described and organized by this category. By following the genealogy of paradigmatic diagrams (such as the phase diagrams in thermodynamics and the curves of magnetization in electrical engineering) or the pedagogical role of squared paper, it is shown how graphical objects came to be valued not just as practical paper tools but as epistemological objects. These two approaches provide the basis for an interpretation of how the historical category of the “graphical” and graphical objects were perceived and valued in the 19th century.