76o THE POPULAR SCIENCE MONTHLY. 



In the mucli-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.* As the colors become whitish, their glar- 

 ing contrast disappears, and they blend more harmoniously into 

 one another. Therefore, under a clear sky, the fiery red petti- 

 coat 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 j^ainted fagades 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 stereo- 

 scope the different manner in which binocular vision distin- 

 guishes 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 dimen- 

 sions 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 hu- 

 man 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 vari- 

 ous 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 diame- 

 ters 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 0, Fourth Part, 1887, pp. 

 284, 285. 



