In the 1830s, 40s, and 50s, the Scottish Romantic astronomer and economist John Pringle Nichol used visual representations to embody and communicate key elements of his theory of evolution as a universal principle. Examining four of the diverse representations that appeared in Nichol's popular science books between 1846 and 1850 reveals some of the rich possibilities of evolutionary imagery in the decades prior to Charles Darwin's On the Origin of Species (1859). Daly examines the way in which Nichol's abstract or metaphorical visual representations—which included line diagrams and imaginative, mythic imagery—were apt vessels for his Romantic evolutionary theory, because a single image could simultaneously represent features of evolution across multiple natural domains, embodying the Romantic concept of the unity of nature and the myriad analogies between its constituent parts. As tools of thought, Daly argues, Nichol's visual representations were perspective-taking devices that made unobservable or only partially observable features of evolutionary change across time and space concretely accessible to his readers. Even as they served to clarify and persuade, however, they generated new ambiguities, such as a fundamental tension between teleology and contingency.
Image: Lithograph of Psyche as evolution, ascending toward a heavenly light on a ladder of ouroboros (a snake eating its own tail) rings representing the cycles of life. From John Pringle Nichol, Views of the Architecture of the Heavens (1850), Plate IX, p. 220 (not numbered) at Part III: Psyche, or Evolution.