196 Prof. Helniholtz — Normal Motions of the [April 14, 



Now combine the two sides of fig. 2 into a stereoscopic combination, 

 either by squinting, or with the help of a stereoscope, and you will see that 

 the white lines of the one coincide exactly with the black lines of the other, 

 as soon as the centres of both the figures coincide, although the vertical 

 lines of the two figures are not parallel to each other. 











































































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to 



Therefore not the realhj vertical meridians of both fields of view corre- 

 spond, as has been supposed hitherto, but the ^^^^^z-ew^ vertical meridians. 

 On the contrary, the horizontal meridians really correspond, at least for 

 normal eyes which are not fatigued. After having kept the eyes a long 



