Chapter I 
THE WORLD OF INVISIBLE LIFE 
T HROUGH a wonderful invention called 
the microscope, we can look into a world 
that our forefathers, a few hundred years ago, 
knew nothing about. They did not even know 
that there was such a world. Yet it is a world 
full of strange and interesting forms of life. 
The word microscope comes from two Greek 
words meaning “small” and “to see.” This 
instrument is simply a brass tube with several 
lenses. A lens is usually made of two pieces 
of fine glass, one thicker in the middle than 
at the edges, and the other thicker at the edges 
than in the middle, the two pieces being care¬ 
fully fastened together. There are one or two 
larger lenses at one end, which is called the eye¬ 
piece, and several smaller lenses at the other 
end, which is called the objective. 
What is a 
microscope? 
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