A gelatin silver print by Étienne-Jules Marey, this work captures the scientific study of movement and mechanical force through the pioneering chronophotographic techniques for which the artist was renowned. The image documents an experiment using a Prony brake, a device used to measure mechanical resistance, recorded at 12 kilograms per rotation. True to Marey's practice of visualizing invisible physical phenomena, the photograph bridges art and science, transforming data and motion into a compelling visual record.