602 



THE SPECIAL SENSES. 



they form with each other a large one ; but for remote objects, the 

 visual axes will become more nearly parallel, and their angle con- 

 sequently smaller. It is on this account that we can always dis- 

 tinguish whether any person at a short distance is looking at us, 

 or at some other object in our direction ; since we instinctively 

 appreciate, from the appearance of the eyes, whether their visual 

 axes meet at the level of our own face. 



In looking at a landscape, accordingly, we do not see the whole 

 of it distinctly at the same moment, but only those parts to which 

 out attention is immediately directed. This is because, in the first 

 place, the focus of distinct vision varies, in each eye, for different 

 distances, as we have seen in a former paragraph, and secondly, 

 because both eyes can only be directed together, at one time, to 

 objects at a certain distance. Thus, when we see the foreground 

 or the middle ground distinctly, the distance is vague and uncer- 

 tain, and when we direct our eyes more particularly to the horizon, 

 objects in the foreground become indistinct. In this way we ap- 

 preciate the difference in distance between the various portions of 

 the landscape, as a whole. In the case of particular objects, we are 

 assisted also by the alteration in their individual characters ; for 

 distance produces a diminution, both in apparent size and in in- 

 tensity of color. 



The combined action of the two eyes is also very valuable, for 

 near objects, in giving us an idea of solidity or projection. For 

 within a certain distance, the visual axes when directed together 



Fig. 163. 



Fig. 164. 



AS SEKN BY THK LEFT EYE. 



AS SEEN BY THE KlGHT EYE. 



fit a solid object, are so convenient that the two eyes do not receive 

 the same image. As in Figs. 163 and 164, which represent a skull 



