The French physicist Etienne-Jules Marey (1830–1904) coined the term 'graphic method' for the array of recording devices that encoded phenomena in patterned lines such as seismographs, and chronophotography, also developed by Eadweard Muybridge (1830–1904). This research puts forward the indexical line as a new concept to locate and analyse how the line was informed by the technology of the ‘graphic method’ in experimental science of the nineteenth century and taken on by the conceptual art movement in the mid-1960s. It presents the redefinition of the line and its concomitant contexts such as drawing, technology, and abstract thinking, anachronistically. That is, dialogically across two time periods that re-assess each other through the scope of the index. Stemming from semiotics and applied to film and photography theory, the index as schematized by Charles S. Peirce (1839 – 1914) is a sign with a direct relation with the ‘real’ as cause between the sign and the thing: the object causes the shadow or the photograph, which are the indices. This notion was applied to the art of the 1970s (Krauss 1977; Doane 1996/2007; Iversen 2017) as a traumatic trace; here, Peirce’s notion is interpreted as a measurable trace to open it up to other potential readings, especially the conceptual project of an ego-less, unemotional array of data constituting the artwork. So, what happens if this type of line originating from technology is in direct relation with the reality it expresses graphically albeit abstractly, like a photograph? And what possibilities does it open up when it shifts to art? Through the case studies of the pioneers of conceptual art, Douglas Huebler and Sol LeWitt, who cross-referenced science, graphic and photographic endeavours across times, the indexical line provides a pathway from the graphic method to graphic expression, by introducing language, technology, maps, diagrams, and sequential photography into artistic practices. What is the consequence of such an introduction of science and technology in artistic formalisation of the artwork from the perspective of the subject (the artist-spectator)
