CHAP, in.] 



SIGHT. 



159 



The retinal images of the spaces from A to B and from B to C 

 are equal and the corresponding primary visual sensations are 

 also equal, but the mental appreciation of A B is interfered 

 with by the concurrent sensations of the several intervening dots 

 and intervals, and this leads to a mental exaggeration of the 

 interval between A and B. So also, if two equal squares 



A B 



FIG. 159. 



(Fig. 159) be marked, one with horizontal and the other with 

 vertical alternate dark and light bands, the former will appear 

 higher, and the latter broader, than it really is. Hence short 

 persons often affect dresses horizontally striped in order to 

 increase their apparent height, and very stout persons avoid 

 longitudinal stripes. Again, when a short person is placed side 

 by side with a tall person, the former appears shorter and the 

 latter taller than each really is. By reason of somewhat similar 

 psychical processes two perfectly parallel lines or bands, each of 



{ 



! 



r 



!i 



' 



FIG. 160. 

 which is crossed by slanting parallel short lines (Fig. 160), wil] 



