Steroscopic Sparkle

There are two stereoscopic photographs, one in white against a black background, and the other in black against a white background. When you have a certain plane in white on one of a stereoscopic pair in black on the other, the combined image seems to sparkle, even though the paper used for the pictures is dull. Such stereoscopic drawings of models of crystals produce the impression of glittering graphite. The sparkle of water, the glisten of leaves and other such things are still more noticeable in stereoscopic photographs when this done. Experiments artificially producing stereoscopic fusion of differently lighted or differently painted surfaces repeat the actual conditions in which we see sparkling objects. Indeed, how does a dull surface differ from a glittering polished one? The first one reflects and diffuses light and so seems identically lighted from every point of observation, while the polished surface reflects light in but one definite direction. Therefore, you get many reflected rays, and with the other practically none, these are precisely the conditions that correspond to the stereoscopic fusion of a white surface with a black one. Evidently, there are bound to be instances in looking at glistening polished surfaces when reflected light unevenly distributed between the eyes of the observer. Consequently, the stereoscopic sparkle proves that experience is paramount in the act during which images fuse bodily.