THE SIMPLE MICROSCOPE 3 



— i.e., 50 X 50. A million times is 1,000 diameters 

 multiplied by 1,000. This magnification is very 

 great, and involves the use of expensive objectives 

 and the most careful manipulation. For the sake 

 of brevity, magnification is represented by the 

 multiphcation sign and the number of diameters : 

 thus X 50 = 50 diameters. 



No matter how impecunious a student may be, 

 he need not be deprived of a lens. Here are two 

 ways in which he may extemporize one at practically 

 no cost. In the first place he may insert a drop of 

 water in a hole in a black card pierced with a red- 

 hot needle. The drop of water wiU form a lens of 

 some magnifying power. Such a lens, of course, is 

 only a temporary expedient. The second way is to 

 make a small circular hole in a black card, and pour 

 into it a drop of warmed Canada balsam, which on 

 coohng will set hard and form a lens. 



Such expedients cannot, however, be taken too 

 seriously ; they can be regarded as curious and 

 experimental, and need be resorted to only as such 

 when we consider that lenses of permanent value 

 can be purchased for a few pence. For a modest 

 sixpence almost any optician will supply a fair 

 magnifying glass in a folding metal mount, suitable 

 for carriage in the waistcoat pocket. This will do 

 good work, and is very suitable for young nature 

 students ; and it need not be disdained by the ex- 

 perienced field-naturahst. It is really remarkable 

 how much is revealed by so simple and inexpensive 

 a tool. 



The uses to which a pocket lens may be put are 

 manifold ; they extend to every department of 



