222 ANSWERS TO PRACTICAL QUESTIONS 



In order to form these judgments correctly, one of 

 these elements must be fixed. From this we learn to 

 institute a comparison, and thus form an accurate 

 opinion. If we know the magnitude of an object, the 

 change in its color and outline will teach us its distance. 

 If we know its distance, we can judge of its magnitude. 

 Hence, painters, in order to give us a correct idea of an 

 object which they represent, always place in its vicinity 

 something with whose real magnitude we are familiar. 

 Thus, to show the size of a pyramid, an Arab with his 

 camel may be drawn at its foot. If the pyramid were 

 represented by itself, its intended size might be mistaken ; 

 but every one knows the size of a camel, and from this 

 he would judge of the magnitude of a pyramid. Way- 

 land 1 s Intellectual Philosophy, p. 78, et seq. 



55. If you sit where you cannot see another person's 

 image, why cannot that person see yours ? 



The angle of incidence is equal to the angle of reflec- 

 tion under all circumstances. If a ray from the other 

 person is not reflected at the right angle to reach your 

 eye, then a ray from you is not reflected at the right 

 angle to reach the other person's eye. 



56. Why can we see the multiple images in a mirror 

 better if we look into it very obliquely ? 



More light is then reflected to the eye. 



(See Physics ) p. 151, 2d note.) 



57. Why is an image seen in water inverted'} 



(Examine Fig. 140, in Physics.) 



58. Why is the surfs light fainter at sunset than at mid- 

 day? 



(See Physics, p. 149, note.) 



