THE PERCEPTION OF THINGS. 95 



greater number are vertical lines. Hence we are peculiarly inclined to 

 think that a line which we perceive to be in such a plane is a vertical 

 line. But to see a lot of lines at once, all ready to throw their images 



Fig. 50. 



upon the vertical meridian, is a thing that has hardly ever happened to 

 us, except when they all have been vertical lines. Hence when that 

 happens we have a still stronger tendency to think that what we see 

 before us is a group of vertical lines." 



In other words, we see, as always, the most probable 

 object. 



The foregoing may serve as examples of the first type 

 of illusions mentioned on page 86. I could cite of course 

 many others, but it would be tedious to enumerate all the 

 thaumatropes and zoetropes, dioramas, and juggler's tricks 

 in which they are embodied. In the chapter on Sensation 

 we saw that many illusions commonly ranged under this 

 type are, physiologically considered, of another sort al- 

 together, and that associative processes, strictly so called, 

 have nothing to do with their production. 



Illusions of the Second Type. 



We may now turn to illusions of the second of the two 

 types discriminated on page 86. In this type we perceive a 

 wrong object because our mind is full of the thought of it 

 at the time, and any sensation which is in the least degree 

 connected with it touches off, as it were, a train already 

 laid, and gives us a sense that the object is really before 

 us. Here is a familiar example : 



" If a sportsman, while shooting woodcock in cover, sees a bird 

 about the size and color of a woodcock get up and fly through the foil- 



