PHYSIOLOGICAL PARADOXES. 



On a larger scale, precisely the same result 

 can be observed without the aid of a microscope. 

 The field which in May looks half a mile off like 

 a huge piece of polished emerald, really con- 

 sists of myriads of separate blades of grass. In 

 July a stretch of the hill-side which presents, 

 across the valley, the appearance of a huge 

 patch of soldiers' scarlet, or of a slice cut out of 

 the blue sky, is actually composed of innumer- 

 able separate flowers of poppy or of lavender. 



We must be always on our guard against 

 thinking that a surface or a substance is con- 

 tinuous because it looks so. The fact is simply 

 that there is a limit to the smallness of things 

 observable by our eyes, and when the size of 

 several contiguous objects is so small or the 

 distance so great that the angle they subtend 

 at the eye passes these limits of smallness, they 

 can no longer make separate impressions, but 

 they unite to produce a common effect, and 

 thus cause an appearance of continuity which 

 has nothing in reality corresponding to it. 



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