NATURAL PHILOSOPHY. Ili7 



RELATION BETWEEN OUR PERCEPTION OF DISTANCE AND 



COLOR. 



The fact that a landscape appears more vivid in color, when viewed 

 by the eyes brought into an abnormal position, as in looking under 

 the arm, etc., is well known. Some persons have attempted to explain 

 this fact by the influence of an augmented pressure of the blood upon 

 the retina. In an easy reclining posture, where such pressure can 

 hardly exist, I observe this heightening of tints with great distinct- 

 ness, also by viewing the inverted image of the landscape by total 

 reflexion through a rectangular prism, the head being in its natural 

 position. Dr. "A. Miiller with more probability has referred this 

 appearance to the different accommodation of the eye for horizontal 

 and vertical lines. To me it seems that this effect is intimately con- 

 nected with our perception or non-perception of distance. In gazing 

 at landscapes, the ordinary habit of most persons, artists excepted, 

 leads them to pay attention to the forms and distances (which alone 

 have a practical value as objects of observation), and to neglect the 

 color, particularly those portions of it which are subdued. When 

 now by any means the mind is prevented from dwelling on distance, 

 it is thrown back on the remaining element, color; and the landscape 

 appears like a mass of beautiful patches of color heaped upon each 

 other, and situated more or less in a vertical plane. 



1. A perpendicular position of the eyes reduces very consider- 

 ably our perception of depth or distance, so that false estimates of it 

 are formed by the eyes in this new situation. With the exception of 

 objects in the foreground, all things seem to lie not far removed from 

 the same vertical plane. 



The reason is partly to be found in the fact, that while in normal 

 vision our binocular perception of depth is obtained by regarding 

 vertical lines, trees, etc., in vertical vision the same objects, though 

 instinctively sought, afford us no information. 



2. In normal vision with a single eye, there is certainly, in a 

 binocular sense, no perception of depth, nevertheless the mind occu- 

 pies itself with the idea of distance, and if the objects are familiar 

 there is no augmentation of color perceived. By inverting the image 

 of the landscape with a rectangular prism the objects fall into almost 

 one plane, are diminished in apparent magnitude, and the mind, 

 unable to trace distances through this maze, is forced to dwell on the 

 mass of tints presented. 



3. With the erecting or inverting telescope, in proportion as the 

 objects viewed are divested of the idea of solidity or depth, can their 

 more delicate tints be perceived. Objects, which in normal vision 

 seem to us nearly without color, are best fitted for these observations ; 

 a bare pile of stones and dry mud viewed through a telescope appears 

 often like a richly tinted water-color drawing. 



It would seem probable that if we could add to paintings of land- 

 scapes the element of distance, the mind, occupied with this, would 

 no longer dwell on the richness of the tints. In confirmation, I find 

 that colored stereographs of landscapes, which out of the stereoscope 

 seem exaggerated in tint, when placed in the instrument no longer 

 appear too highly colored. 



