Superpositions: Ludwig Mach and Étienne-Jules Marey’s studies in streamline photography

In the 1890s Ludwig Mach (the first-born son of Ernst Mach) employed photography for visualizing streamlines in the emerging field of aerodynamic research. Étienne-Jules Marey developed a similar approach at the turn of the century. The two projects can be related to a number of current discussions on the history of scientific photography. (1) The case of Ludwig Mach demonstrates how the collection of numerical data became both the subject and the challenge of a line of research intimately linked to the capacities of photography. (2) At the end of the nineteenth century, the particular potential of scientific photography is very often defined by comparison with the limited power of the human eye. In contrast, the example of streamline photography underlines that the requirements of the research context are critical for successfully employing photography. (3) Marey’s studies point to a tension between his characterization of chronophotography as a method for analyzing the elementary units of processes in nature on the one hand and the necessary summation of single moments in time in his recordings of streamlines on the other. What Marey usually qualified as a cumbersome confusion was here the prerequisite of observation. (4) The ’philosophy in machines’ (Peter Galison) ultimately limited the success of streamline photography; it aided in debates about qualitative matters, but could hardly provide what most interested scientists and engineers: reliable numbers.

► The potential of photography in scientific observation depends on the research context.
► The problem of quantification limits the usage of photography in the context of scientific research.
► Streamline photography proved to be a secondary and only supplementary tool in early aerodynamic research.