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THE POPULAR SCIENCE MONTHLY. 



ing is broadened and the arches are apparently wider than is 

 shown in Fig. 2. 



In all these pictures the frame also is worthy of notice. In 

 the first it has its true proportions; and in the second, it is dis- 

 torted at the sides, and in the third, above and below. 



There can be no question but that astigmatism even in a slight 

 degree materially affects what the artist sees, and if it is true that 

 he draws what he sees, does this not mean that his drawing tends 

 to be proportionately faulty ? Nor does it affect the vision for 

 rectangular objects alone. This distortion is a constant quantity, 

 and it does not take very exact study to see its effect in the draw- 



FlG. 3. 



ing of the figure. For this reason, often an undue plumpness is 

 given to some portions, while others are rendered emaciated and 

 anaemic to a degree of which the originals were never guilty. 



Another disadvantage of astigmatism to the artists is that 

 lines really parallel appear to converge or diverge, when distorted 

 by the blurring which astigmatism can produce. The reason of 

 this would require too great a digression here. The practical fact 

 is that as the blurring is unequal when different parts of the 

 objects are differently illuminated, and as the direction of the 

 apparent blurs depends somewhat upon the form of the object, 

 lines which should be straight have their direction apparently 

 changed. 



