Page:Popular Science Monthly Volume 1.djvu/190

180 for instance, have a normal refraction in its horizontal meridian, and be short-sighted in its vertical meridian. Small differences of this kind are found in almost every eye, but are not perceived. Higher degrees of astigmatism, which decidedly disturb vision, are, however, not uncommon, and are, therefore, also found among painters. I have had occasion to examine the eyes of several distinguished artists which presented such an anomaly, and it interested me much to discover what influence this defect had upon their works. The diversity depends in part upon the degree and nature of the optical anomaly, but its effect shows itself in different ways, according to the subjects the artist paints. An example will explain this better. I know a landscape-painter and a portrait-painter who have both the same kind of astigmatism; that is, the refraction of the vertical meridian differs from the refraction of the horizontal one. The consequence is, that their sight is normal for vertical lines, but for horizontal lines they are

slightly short-sighted. Upon the landscape-painter this has hardly any disturbing influence. In painting distant views, sharp outlines are not requisite, but rather undefined and blending tones of color. His eye is sufficiently normal to see these. I was struck, however, by the fact that the foreground of his pictures, which generally represents water with gently-moving waves, was not painted with the same truthfulness to Nature as the middle and background. There I found short horizontal strokes of the brush In different colors, which did not seem to belong to the water. I therefore examined the picture with a glass, which, when added to my eye, produced the same degree of astigmatism as existed in the painter's eye, and the whole picture appeared much more beautiful, the foreground being now as perfect as the middle and background. In consequence of this artificially-produced astigmatism, I saw the horizontal strokes of the brush indistinctly,