How does a 
microscope wor\? 
12 WORLD OF INVISIBLE LIFE 
All of these lenses can be changed about, 
so that whatever is to be examined may be 
enlarged to exactly the right size to enable us 
to see it clearly. 
The brass tube is fastened to a stand which 
holds it upright, and which has a little table 
with a hole in its center just below the end 
of the tube. A mirror below throws light 
through this hole into the brass tube. What¬ 
ever is to be examined is put on a glass plate 
called a slide, which is then fastened to the 
little table. A moment later, when we put our 
eye to the larger lens at the top and look down 
through the tube, we see a clear picture, many 
times enlarged. 
A microscope such as those used by scientists 
in their laboratories is not so simple as ordinary 
microscopes, and costs a great deal of money. 
Such a microscope is often so powerful that it 
can enlarge things hundreds and even thou¬ 
sands of times their real size. 
If we take some cloudy water from a pond 
into the laboratory and put a drop of it on 
