Ill 



beholds. It appears to it most probably, not on the retina, 

 Avhere the rays of light form its resemblance, and create a 

 sensation ; but where the circle actually exists, the aperture 

 of the ^ye. Afterward the walls and furniture and inmates 

 of its apartment, or the scenery and animation of an exten- 

 sive prospect, reduced to an almost imperceptible miniature, 

 occupy the same narrow field of view : one object indistin- 

 guishable, on account of its minuteness from another, but 

 forming altogether an intermingled mass of brilliant colours. 

 This variegated tissue is changed to one dull unvaried colour, 

 when an object approaches so near as to occupy the field of 

 view to the exclusion of other objects. Distance is as yet 

 imperceptible to the eye, and inconceivable by the mind. 

 The hand must be often extended and withdrawn, placed be- 

 fore the eye and on different parts of the body, contem- 

 plated in different positions and at different distances, before 

 the infant ascertains that the hand which it beholds is that 

 which a repetition of the sensations of feeling had previously 

 taught it to regard as part of its frame. This is the first step 

 in the complicated process by which it acquires the habit 

 of judging of distances : for the hand is the first measure it 

 uses, and it must be familiar with the instrument before it 

 can employ it with effect. 



In time he discovers that the space where his hand moves 

 with freedom is destitute of objects ; and thus ascertains that 

 those which he beholds and cannot touch, lie beyond the ex- 

 tent of his arm. At this period it is probable that the field 



