228 



THE EYE 



opposite picture. By means of this apparatus we obtain a single 

 picture in the most pronounced relief, and situated apparently 



at P. 



p 



p, 



FIG. 55. Diagram of stereoscope. 



We may summarise the advantages of binocular vision as 

 follows : 



(i) The visual field is increased, 

 (ii) We receive impressions of solidity. 



(iii) We have a most important means of judging distances 

 (iv) The loss of one eye does not reduce us to blindness 



