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CHAPTER I 
THE SIMPLE MICROSCOPES 
The construction and use of the simple microscope (magni- 
fiers) undoubtedly date back to very early times. There is 
sufficient evidence to prove that spheres of glass were used as 
burning spheres and as magnifiers by people antedating the 
Greeks and Romans. 
The simple microscopes of to-day have a very wide range of 
application and a corresponding variation in structure and in 
appearance. 
Simple microscopes are used daily in classifying and studying 
crude drugs, testing linen and other cloth, repairing watches, 
in reading, and identifying insects. ‘The more complex simple 
microscopes are used in the dissection and classification of 
flowers. 
' The watchmaker’s loupe, the linen tester, the reading glass, 
the engraver’s lens, and the simplest folding magnifiers consist 
of a double convex lens. Such a lens produces an erect, en- 
larged image of the object viewed when the lens is placed so 
- that the object is within its focal distance. The focal distance 
of a lens varies according to the curvature of the lens. The 
greater the curvature, the shorter the focal distance and the 
greater the magnification. 
The more complicated simple microscope consists of two or 
more lenses. The double and triple magnifiers consist of two 
and three lenses respectively. 
When an object is viewed through three lenses, the magnifi- 
cation is greater than when viewed through one or two lenses, 
but a smaller part of the object is magnified. 
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