ON THE RELATION OF NATURAL SCIENCE TO ART. 669 
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lenses or a high degree of astigmatism might easily lead a painter to 
distort or blur objects he was copying from nature. Donder’s stenoptic 
spectacles or cylindrical spectacles, as the case might be, would prove 
as useful to such an artist as concave glasses to the short-sighted. 
The singularities of another English painter, Mulready, are accounted 
for by Dr. Liebreich through discoloration of the lens from old age. 
Another defect of the eye, color-blindness, ought to be mentioned here, 
which in its milder forms is of frequent occurrence, and even belongs to 
the normal condition of the eye on the borders of the field of vision. 
It corresponds in the domain of hearing to the want of musical ear. 
Color-blindness was known long ago, but has been inquired into with 
redoubled zeal latterly, partly with regard to its general connection 
with chromaties, partly on account of its serious practical consequences 
in the case of sailors, railway officials, and, as Dr. Liebreich adds, of 
painters. Both color-blindness and want of ear are inborn defects, for 
which there is no remedy. <A color-blind artist is however better off 
than a musician without an ear, if such a one were imaginable, for, 
even if he neglected the mahl-stick and the chisel, he might still seek 
his fortune in the designing of cartoons. 
It is difficult to determine the particular point where optical knowl- 
edge ceases to be of use to artists. None will repent having studied 
the laws of the movement of the eyes, the difference between near and 
distant vision, and the observations on the expression of the human 
eye contained in John Miiller’s early work on ‘* Comparative Physiology 
of Sight.” Yet it must be admitted that a painter may paint an eye 
exceedingly well without ever having heard of Sanson’s images, which 
cause the soft luster of a gentle eye as well as the fierce flash of an 
angry one; as little as the blue sky of a landscape painter will gain by his 
knowledge of the yellow brushes in every great circle of the heavenly 
vault which passes through the sun—a phenomenon which has remained 
unnoticed for countless ages, but has grown familiar to physiologists 
since Haidinger’s discovery. 
One point, however, where physicists seem to me not to have been 
sufficiently consulted is the much-debated question of polychrome in 
ancient statues and architecture, and whether it should be adopted by 
modern art or not. Physical experiments teach that very intense 
illumination causes all colors to appear whitish; in the spectrum of the 
sun, seen immediately through the telescope, the colors vanish almost 
entirely, nothing remaining except a light yellow hue in the red end. 
As the colors grow whitish the glaring contrasts are softened, they 
blend more harmoniously. In the open air, therefore, our eye is not 
shocked by the scarlet skirt of the contadina, which recurs almost as 
invariably in Oswald Achenbach’s Campagna landscapes, as the white 
horse in Wouvermann’s war scenes. The Greek statues and buildings 
may have looked well enough with their glaring decorations under the 
bright southern sky on the Acropolis or in the Poikile; in the dull light 
