The Victorians' fascination with the act of seeing has been pointed out by recent scholarship from a variety of critical perspectives. The slipperiness of the borderline between the visible and the invisible, hinted at by the fundamental metaphor of the 'horizon' in the cultural and literary background of the nineteenth century, is the main focus of this text. Bearing on a long and well established area of enquiry that has stressed the interrelationships between literature and science, this study offers an investigation of such essential narratological categories as 'point of view' and 'focalization', as theorized by Henry James, within a wider theoretical, cultural and scientific background that significantly contributed to redefining the visible universe in the light of the new discoveries on the physiology and on the psychology of vision.