I 



USE OF TWO GOOD EYES 13 



advantage of possessing two good eyes is much 

 greater than at first sight may appear. By their 

 joint aid, we are able to place any object in its 

 actual relation to other objects, and to gather a 

 far more exact notion of its size. With one eye, 

 everything appears '* flat," i.e., in one plane. A 

 little experiment will serve to show how useful is 

 the power of stereoscopic sight. Try to thread a 

 needle with both eyes open, and it is a compara- 

 tively simple task, as it is easy to place the thread 

 exactly opposite the eye of the needle; try to do 

 the same with one eye closed, and it will be found 

 much more difficult. 



People with two good eyes should have no 

 trouble in pouring out a glass of wine; people with 

 one eye will often pour the wine upon the cloth and 

 not into the glass, because in holding the bottle 

 above the glass they cannot tell whether it is 

 exactly above it, or slightly nearer or further from 

 them than the glass. 



And here is a little parlour trick which may be 

 played at an evening party and will give some 

 amusement, whilst showing again the disadvantage 

 of seeing with one eye. Place a sixpence on the 

 edge of the table, so that a touch with the finger 

 will send it to the floor. Stand away from the 

 table at such a distance that by slightly bending 

 forward and keeping the arm straight you can 

 just reach the coin with the forefinger of the right 



