In the much-debated question of the polychromy of the ancient statues and buildings, on the contrary, and of the propriety of adopting it, one observation of the physicists, as appears to me, has not hitherto been sufficiently considered. It is that all colors become whitish under a very strong illumination, so that, on the immediate view of the solar spectrum in the telescope, nearly every impression of color disappears, except for a light-yellow shimmer at the red end.[1] As the colors become whitish, their glaring contrast disappears, and they blend more harmoniously into one another. Therefore, under a clear sky, the fiery red petticoat of the Contadina, which is repeated so often in Oswald Achenbach's Campagna pictures, as well as the white horse of Wouverman's war-scenes, make no disagreeable impression on the eye. Under the bright Grecian sky, on the Acropolis, in the Poikile, the more or less glaringly painted façades and pillars still had a pleasant effect; in the gray northern light, and in closed rooms, they are not happily introduced.
Wheatstone has materially enriched the capacity of drawing and painting art from another side, by showing with his stereoscope the different manner in which binocular vision distinguishes nearer objects from monocular vision, and also from the binocular vision of objects so remote that the interval between the eyes vanishes before their distance. The impression of a solid body arises only when each of the eyes receives a different view of the object, and is produced by both views blending into one, the corporeal view. Therefore the painter, expressing dimensions of depth only through shading and air-perspective, has never been able to produce a real corporeal appearance on his canvas. While, then, Wheatstone's pseudoscope shows the human face concave in an unusual way, Helmholtz's telestereoscope exaggerates the distance between the eyes, and, without aerial perspective, resolves the far-off forest or mountain into its various elements. The stereoscope with movable pictures, however, confirms old Dr. Robert Smith's explanation of the fact that the moon and sun appear larger by nearly two tenths of their diameters in the horizon than in the zenith, and reduces the problem to the question why we see the vault of the sky rather flattened like a watch-glass than as a hemisphere.
Of vastly greater importance for art is photography, which originated at nearly the same time with the spectroscope. To fasten Delia Porta's charming pictures was indeed a dream of artists as well as of physicists, and after the discovery of chloride of silver the no longer unattainable object came in sight. One
- ↑ Helmholtz, Handbuch der physiologischen Optic, A. a O, Fourth Part, 1887, pp. 284, 285.
