VISION 403 



The mind does not look at the retina. If it did, it would find 

 the reversal of the picture the least of the inaccuracies which 

 it had to correct. It would find it very difficult, for example, 

 to superpose in its stereoscope the photographs of a vertical 

 tower taken simultaneously by the right eye and the left. The 

 curved images on the retina of the vertical lines which deftne 

 the angles of the tower, as seen with one eye, could not be 

 made to correspond with the images focussed by the other eye. 

 The Greeks felt this when they settled the form of a column. 

 The canon of the swelling entasis and increasing taper above 

 it did not destroy the appearance of uniform thickness which 

 the shaft presented. It gave to the eye just the slight help 

 which it needs to enable it to picture the shaft as of the same 

 thickness from base to capital. 



262 



