CH. XV] DEMONSTRATING REFRACTIVE EYE DEFECTS 667 



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 = r-a Si.i -_. EC 



FIG. 394, 395. FIGURES SHOWING THE APPEARANCE OF THE RADIAL LINES 

 AND OF PRINTED MATTER WHEN AN ASTIGMATIC LENS is IN Focus FOR 

 HORIZONTAL LINES. 



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ASTIGMATISM 



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ll.ivnl 'in. l-ly. 111(11 



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FIG. 396, 397. FIGURES SHOWING THE APPEARANCE OF THE RADIAL LINES 

 AND PRINTED MATTER WHEN THE ASTIGMATIC LENS is IN Focus FOR 



VERTICAL LINES. 



Figures 394-397 were made by adding a +.5 cylindrical lens to a +5.5 

 diopter photographic objective, and the cylinder was placed with its axis 

 vertical in fig. 394-395, and horizontal in fig. 396 and 397; no change was 

 made in the focus of the objective. The aperture of the objective was F/i6 

 when the photograph was made. 



As shown in figures 395-397, Gothic print seen through an astigmatic lens is 

 clearer when the axis is such that the vertical lines are in focus. This is 

 because the vertical lines are more numerous than the horizontal lines. 



